Gateway S466, ADAC ULTRA2 S466 User Manual
Loading...ADAC Ultra2 S466
Single Ended and Low-
Voltage Differential SCSI
PCI RAID Controller
Hardware Guide
8503624 A MAN US ADAC U2 S466 GDE R0 8/14/98
© Copyright 1998 Gateway, Inc. All rights reserved.
This publication contains proprietary information which is protected by copyright. No part of this publication can be reproduced, transcribed, stored in a retrieval system, translated into any language or computer language, or transmitted in any form whatsoever without the prior written consent of the publisher, Gateway, Inc. Gateway, Inc. acknowledges the following trademarks:
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Revision History
6/8/98 Initial release.
ii ADAC Ultra2 S466 Hardware Guide
Table of Contents |
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1 Overview ............................................................... |
1 |
Single Ended and Differential SCSI Buses .............................. |
2 |
Maximum Cable Length for SCSI Standards ........................... |
2 |
Documentation ......................................................................... |
3 |
ADAC Ultra2 S466 Block Diagram......................................... |
4 |
2 Introduction to RAID ............................................ |
5 |
RAID Benefits.......................................................................... |
5 |
In This Chapter......................................................................... |
6 |
ADAC Ultra2 S466 – Host-Based RAID Solution................... |
7 |
RAID Overview ....................................................................... |
8 |
Consistency Check ................................................................... |
8 |
Fault Tolerance ........................................................................ |
8 |
Disk Striping ............................................................................ |
9 |
Disk Spanning ........................................................................ |
10 |
Disk Mirroring ....................................................................... |
11 |
Parity ...................................................................................... |
12 |
Hot Spares .............................................................................. |
13 |
Disk Rebuild........................................................................... |
14 |
Logical Drive ......................................................................... |
15 |
Hot Swap................................................................................ |
15 |
SCSI Drive States................................................................... |
16 |
Logical Drive States ............................................................... |
16 |
Disk Array Types ................................................................... |
17 |
Enclosure Management .......................................................... |
17 |
3 RAID Levels ........................................................ |
19 |
Selecting a RAID Level ......................................................... |
20 |
RAID 0 ................................................................................... |
21 |
RAID 1 ................................................................................... |
22 |
RAID 3 ................................................................................... |
23 |
RAID 5 ................................................................................... |
25 |
RAID 10 ................................................................................. |
26 |
RAID 30 ................................................................................. |
27 |
RAID 50 ................................................................................. |
28 |
4 ADAC Ultra2 S466 Features .............................. |
29 |
Hardware Requirements ......................................................... |
30 |
Configuration Features ........................................................... |
30 |
Hardware Architecture Features............................................. |
31 |
Array Performance Features................................................... |
31 |
RAID Management Features .................................................. |
32 |
Fault Tolerance Features ........................................................ |
32 |
Contents |
iii |
Software Utilities.................................................................... |
33 |
Operating System Software Drivers ....................................... |
33 |
ADAC Ultra2 S466 Specifications......................................... |
34 |
PCI Bridge/CPU..................................................................... |
35 |
Cache Memory ....................................................................... |
35 |
ADAC Ultra2 S466 BIOS ...................................................... |
35 |
Onboard Speaker.................................................................... |
36 |
Serial Port............................................................................... |
36 |
SCSI Bus ................................................................................ |
36 |
SCSI Connectors .................................................................... |
37 |
SCSI Termination................................................................... |
37 |
SCSI Firmware ....................................................................... |
37 |
RAID Management ................................................................ |
38 |
Fault-Tolerance Features........................................................ |
39 |
Compatibility.......................................................................... |
40 |
Summary ................................................................................ |
40 |
5 Configuring ADAC Ultra2 S466 ......................... |
41 |
Configuring SCSI Physical Drives ......................................... |
41 |
Current Configuration ............................................................ |
42 |
Logical Drive Configuration .................................................. |
42 |
Physical Device Layout.......................................................... |
43 |
Configuring Arrays................................................................. |
45 |
Configuration Strategies......................................................... |
46 |
Assigning RAID Levels.......................................................... |
48 |
Configuring Logical Drives.................................................... |
48 |
Optimizing Data Storage ........................................................ |
49 |
Planning the Array Configuration .......................................... |
50 |
Array Configuration Planner .................................................. |
51 |
6 Hardware Installation......................................... |
53 |
Checklist................................................................................. |
53 |
Installation Steps .................................................................... |
54 |
Step 1 Unpack ........................................................................ |
55 |
Step 2 Power Down................................................................ |
55 |
Step 3 Configure Motherboard............................................... |
55 |
Step 4 Install Cache Memory ................................................. |
56 |
Step 5 Set Jumpers ................................................................. |
58 |
ADAC Ultra2 S466 Card Layout ........................................... |
58 |
Step 6 Set Termination........................................................... |
61 |
SCSI Termination................................................................... |
62 |
Step 7 Install ADAC Ultra2 S466 .......................................... |
65 |
Step 8 Connect SCSI Cables .................................................. |
66 |
Step 9 Set Target IDs ............................................................. |
67 |
Device Identification on ADAC Ultra2 S466......................... |
68 |
Step 10 Power Up .................................................................. |
69 |
iv ADAC Ultra2 S466 Hardware Guide
Step 11 Run ADAC BIOS Setup............................................ |
70 |
Step 12 Install Operating System Driver ................................ |
70 |
Summary ................................................................................ |
72 |
7 Troubleshooting................................................. |
73 |
BIOS Boot Error Messages .................................................... |
75 |
Other BIOS Error Messages................................................... |
77 |
DOS ASPI Driver Error Messages ......................................... |
78 |
Other Potential Problems ....................................................... |
79 |
A SCSI Cables and Connectors............................ |
83 |
SCSI Connectors .................................................................... |
83 |
68-Pin High Density SCSI Internal Connector....................... |
83 |
High-Density 68-Pin SCSI Connector Pinout ........................ |
89 |
68-Pin Connector Pinout for LVD SCSI ................................ |
91 |
B Audible Warnings ............................................... |
93 |
Index........................................................................ |
95 |
Contents |
v |
Preface
The ADAC Ultra2 S466 PCI RAID Controller supports all single ended and low-voltage differential (LVD) SCSI devices on an Ultra and Wide SCSI channel with data transfer rates up to 80 MB/s (Megabytes per second). This manual describes ADAC Ultra2 S466.
Limited Warranty The buyer agrees if this product proves to be defective, that Gateway is only obligated to repair or replace this product at Gateway’s discretion according to the terms and conditions of the warranty registration card that accompanies this product. Gateway shall not be liable in tort or contract for any loss or damage, direct, incidental or consequential resulting from the use of this product. Please see the Warranty Registration Card shipped with this product for full warranty details.
Limitations of Liability Gateway, Inc. shall in no event be held liable for any loss, expenses, or damages of any kind whatsoever, whether direct, indirect, incidental, or consequential (whether arising from the design or use of this product or the support materials provided with the product). No action or proceeding against Gateway may be commenced more than two years after the delivery of product to Licensee of Licensed Software.
Licensee agrees to defend and indemnify Gateway from any and all claims, suits, and liabilities (including attorney’s fees) arising out of or resulting from any actual or alleged act or omission on the part of Licensee, its authorized third parties, employees, or agents, in connection with the distribution of Licensed Software to end-users, including, without limitation, claims, suits, and liability for bodily or other injuries to end-users resulting from use of Licensee’s product not caused solely by faults in Licensed Software as provided by Gateway to Licensee.
Cont’d
Preface |
vii |
Preface, Continued
Package Contents You should have received:
∙a ADAC Ultra2 S466 PCI RAID Controller,
∙a ADAC Ultra2 S466 Hardware Guide,
∙a ADAC Ultra2 S466 Configuration Software Guide,
∙a ADAC Ultra2 S466 Operating System Drivers Guide,
∙software license agreement,
∙diskette(s) with the ADAC Ultra2 S466 software, and
∙a warranty registration card.
Technical Support If you need help installing, configuring, or running the ADAC Ultra2 S466 PCI RAID Controller, call your Gateway OEM Technical Support representative. For the current number, refer to the Assistance Resources Brochure that was included with your system. Before you call, please complete the ADAC Ultra2 S466 Problem Report form on the next page.
Web Site |
We invite you to access the Gateway world wide web site |
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at: |
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http://www.gateway.com. |
viii ADAC Ultra2 S466 Hardware Guide
ADAC Ultra2 S466 Problem Report Form
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Customer Information |
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ADAC Ultra2 S466 Information |
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Name |
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Today’s Date |
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Company |
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Date of Purchase |
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Address |
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Invoice Number |
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City/State |
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Serial Number |
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Country |
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email address |
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Cache Memory |
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Phone |
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Firmware Version |
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Fax |
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BIOS Version |
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System Information |
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Motherboard:
Operating System:
Op. Sys. Ver.:
ADAC Ultra2 S466
Driver Ver.:
Network Card:
Other disk controllers installed:
Description of problem:
BIOS manufacturer:
BIOS Date:
Video Adapter:
CPU Type/Speed:
System Memory:
Other adapter cards installed:
Steps necessary to re-create problem: 1.
2.
3.
4.
Logical Drive Configuration
Logical |
RAID |
Stripe |
Logical Drive |
Cache |
Read |
Write |
# of Physical |
Drive |
Level |
Size |
Size |
Policy |
Policy |
Policy |
Drives |
LD1
LD2
LD3
LD4
LD5
LD6
LD7
LD8
Preface |
ix |
Physical Device Layout
Channel 1
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
x ADAC Ultra2 S466 Hardware Guide
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Target ID
Device Type
Logical Drive Number/ Drive Number
Manufacturer/Model Number
Firmware level
Channel 1
Preface |
xi |
Preface, Continued
Disclaimer |
This manual describes the operation of the Gateway ADAC |
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Ultra2 S466 Disk Array Controller. Although efforts have been |
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made to assure the accuracy of the information contained here, |
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Gateway expressly disclaims liability for any error in this |
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information, and for damages, whether direct, indirect, special, |
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exemplary, consequential or otherwise, that may result from such |
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error, including but not limited to the loss of profits resulting |
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from the use or misuse of the manual or information contained |
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therein (even if Gateway has been advised of the possibility of |
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such damages). Any questions or comments regarding this |
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document or its contents should be addressed to Gateway at the |
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address shown on the cover. |
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Gateway provides this publication “as is” without warranty of |
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any kind, either expressed or implied, including, but not limited |
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to, the implied warranties of merchantability or fitness for a |
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specific purpose. |
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Some states do not allow disclaimer of express or implied |
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warranties or the limitation or exclusion of liability for indirect, |
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special, exemplary, incidental or consequential damages in |
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certain transactions; therefore, this statement may not apply to |
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you. Also, you may have other rights which vary from |
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jurisdiction to jurisdiction. |
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This publication could include technical inaccuracies or |
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typographical errors. Changes are periodically made to the |
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information herein; these changes will be incorporated in new |
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editions of the publication. Gateway may make improvements |
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and/or revisions in the product(s) and/or the program(s) |
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described in this publication at any time. |
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Requests for technical information about Gateway products |
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should be made to your Gateway representative. |
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xii ADAC Ultra2 S466 Hardware Guide
FCC Regulatory Statement
This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
Warning: Changes or modifications to this unit not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment.
Note: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a specific installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, try to correct the interference by one or more of the following measures:
1)Reorient or relocate the receiving antenna.
2)Increase the separation between the equipment and the receiver.
3)Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
4)Consult the dealer or an experienced radio/TV technician for help.
Shielded interface cables must be used with this product to ensure compliance with the Class B FCC limits.
Gateway ADAC Ultra2 S466 PCI RAID Controller
Model Number: |
Series 466 |
FCC ID Number: |
IUESER466 |
Preface |
xiii |
Disclaimer
Gateway only certifies that this product will work correctly when this product is used with the same jumper settings, the same system configuration, the same memory module parts, and the same peripherals that were tested by Gateway with this product. The complete list of tested jumper settings, system configurations, peripheral devices, and memory modules are documented in the Gateway Compatibility Report for this product. Call your Gateway sales representative for a copy of the Compatibility Report for this product.
xiv ADAC Ultra2 S466 Hardware Guide
1 Overview
The ADAC Ultra2 S466 PCI RAID controller is a high performance intelligent PCI-to-SCSI host adapter with RAID control capabilities. The ADAC Ultra2 S466 provides reliability, high performance, and fault-tolerant disk subsystem management. The ADAC Ultra2 S466 is an entry level-to mid-range RAID controller solution. ADAC Ultra2 S466 offers a cost-effective way to implement RAID in a server. The ADAC Ultra2 S466 has an Ultra and Wide SCSI channel supporting data transfer rates up to 80 Megabytes per second (MB/s) per channel. The SCSI channel supports up to fifteen non-Ultra SCSI devices.
ADAC Ultra2 S466 Features ADAC Ultra2 S466 features:
∙provides a high performance I/O migration path while preserving existing PCI-SCSI software,
∙Performs SCSI data transfers up to 80 MB/s,
∙performs synchronous operation on a wide LVD SCSI bus,
∙allows up to 15 LVD SCSI devices on the wide bus,
∙includes an Intel® i960RP that performs RAID calculations and routing and
∙supports 4, 8, 16, 32, 64, or 128 MB of Fast Page Mode or EDO DRAM cache memory in a SIMM socket used for read and write-back caching and RAID 5 parity generation.
SCSI Channel The ADAC Ultra2 S466 upgrade card includes one Fast-20 SCSI channel. The channel is powered by a Symbios Logic 53C895 (Fast-40) SCSI processor.
NVRAM and Flash ROM A 32 KB x 8 NVRAM stores RAID system configuration information. The ADAC Ultra2 S466 firmware is stored in flash ROM for easy upgrade.
SCSI Connectors ADAC Ultra2 S466 has one ultra high density 68-pin external connector for external storage subsystem and one high density 68-pin internal connector.
Chapter 1 Overview |
1 |
Single Ended and Differential SCSI Buses
The SCSI standard defines two electrical buses:
∙a single ended bus and
∙low-voltage differential bus.
Maximum Cable Length for SCSI Standards
Standard |
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Single ended |
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LVD |
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Maximum Number |
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of Drives |
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SCSI I |
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6 m |
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12 m |
7 |
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Fast SCSI |
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6 m |
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12 m |
7 |
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Fast Wide SCSI |
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6 m |
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12 m |
15 |
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Ultra SCSI |
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1.5 m |
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12 m |
7 |
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Ultra SCSI |
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3 m |
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12 m |
3 |
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Wide Ultra SCSI |
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12 m |
15 |
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Wide Ultra SCSI |
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1.5 m |
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12 m |
7 |
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Wide Ultra SCSI |
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3 m |
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12 m |
3 |
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Ultra 2 SCSI |
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25 m |
1 |
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Ultra 2 SCSI |
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12 m |
7 |
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Wide Ultra 2 SCSI |
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25 m |
1 |
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Wide Ultra 2 SCSI |
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12 m |
15 |
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SCSI Bus Widths and Maximum Throughput
SCSI Standard |
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SCSI Bus Width |
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SCSI Throughput |
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SCSI I |
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8 bits |
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5 MB/s |
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Fast SCSI |
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8 bits |
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10 MB/s |
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Fast Wide SCSI |
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16 bits |
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20 MB/s |
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Ultra SCSI |
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8 bits |
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20 MB/s |
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Wide Ultra SCSI |
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16 bits |
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40 MB/s |
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Ultra 2 SCSI |
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8 bits |
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40 MB/s |
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Wide Ultra 2 SCSI |
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16 bits |
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80 MB/s |
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2 ADAC Ultra2 S466 Hardware Guide
Documentation
The ADAC Ultra2 S466 documentation set includes:
Using ADAC Ultra2 S466 Manuals This manual contains the RAID overview, RAID planning, and RAID system configuration information you will need first. Read the ADAC Ultra2 S466 Hardware Guide first.
ADAC Ultra2 S466 Configuration Software Guide This manual describes the software configuration utilities that configure and modify RAID systems.
ADAC Ultra2 S466 Operating System Drivers Guide This manual provides detailed information about installing the ADAC Ultra2 S466 operating system drivers.
Chapter 1 Overview |
3 |
ADAC Ultra2 S466 Block Diagram
4 ADAC Ultra2 S466 Hardware Guide
2 Introduction to RAID
RAID (Redundant Array of Independent Disks) is an array of multiple independent hard disk drives that provide high performance and fault tolerance. A RAID disk subsystem improves I/O performance over a computer using only a single drive. The RAID array appears to the host computer as a single storage unit or as multiple logical units. I/O is expedited because several disks can be accessed simultaneously. RAID systems improve data storage reliability and fault tolerance compared to single-drive computers. Data loss because of a disk drive failure can be recovered by reconstructing missing data from the remaining data and parity drives.
RAID Benefits
RAID has gained popularity because it: improves I/O performance, and increases storage subsystem reliability. RAID provides data security through fault tolerance and redundant data storage. The ADAC Ultra2 S466 management software configures and monitors RAID disk arrays.
Improved I/O Although disk drive capabilities have improved drastically, actual performance has improved only three to four times in the last decade. Computing performance has improved over 50 times during the same time period.
Increased Reliability The electromechanical components of a disk subsystem operate more slowly, require more power, and generate more noise and vibration than electronic devices. These factors reduce the reliability of data stored on disks.
Chapter 2 Introduction to RAID |
5 |
In This Chapter
The following topics are discussed:
Major Topic |
Subtopic |
turn to |
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Host-based solution |
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page 7 |
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RAID overview |
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page 8 |
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Consistency check |
page 8 |
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Fault tolerance |
page 8 |
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Disk striping |
page 9 |
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Disk spanning |
page 10 |
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Disk mirroring |
page 11 |
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Parity |
page 12 |
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Hot spares |
page 13 |
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Disk rebuilds |
page 14 |
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RAID levels |
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page 19 |
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Selecting a RAID level |
page 20 |
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RAID 0 |
page 21 |
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RAID 1 |
page 22 |
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RAID 3 |
page 23 |
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RAID 5 |
page 25 |
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RAID 10 |
page 26 |
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RAID 30 |
page 27 |
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RAID 50 |
page 28 |
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6 ADAC Ultra2 S466 Hardware Guide
ADAC Ultra2 S466 – Host-Based RAID Solution
RAID products are either:
∙host-based or
∙SCSI-to-SCSI.
The ADAC Ultra2 S466 controller is a host-based RAID solution. ADAC Ultra2 S466 is a PCI adapter card that is installed in any available PCI expansion slot in a host system.
Host-Based A host-based RAID product puts all of the RAID intelligence on an adapter card that is installed in a network server. A host-based RAID product provides the best performance. ADAC Ultra2 S466 is part of the file server, so it can transmit data directly across the computer’s buses at data transfer speeds up to 132 MB/s.
The available sequential data transfer rate is determined by the following factors:
∙the sustained data transfer rate on the motherboard PCI bus,
∙the sustained data transfer rate on the i960RP PCI to PCI bridge,
∙the sustained data transfer rate of the SCSI controller,
∙the sustained data transfer rate of the SCSI devices,
∙the number of SCSI channels, and
∙the number of SCSI disk drives.
Host-based solutions must provide operating systemspecific drivers.
SCSI-to-SCSI A SCSI-to-SCSI RAID product puts the RAID intelligence inside the RAID chassis and uses a plain SCSI Host Adapter installed in the network server. The data transfer rate is limited to the bandwidth of the SCSI channel. A SCSI-to-SCSI RAID product that has two wide SCSI channels that operate at speeds up to 80 MB/s must squeeze the data into a single wide SCSI (40 MB/s) channel back to the host computer.
In SCSI-to-SCSI RAID products, the hard drive subsystem uses only a single SCSI ID, which allows you to connect multiple drive subsystems to a single SCSI controller.
Chapter 2 Introduction to RAID |
7 |
RAID Overview
RAID (Redundant Array of Independent Disks) is a collection of specifications that describe a system for ensuring the reliability and stability of data stored on large disk subsystems. A RAID system can be implemented in a number of different versions (or RAID Levels). The standard RAID levels are 0, 1, 3, and 5. ADAC Ultra2 S466 supports all standard RAID levels and RAID levels 10, 30, and 50, special RAID versions supported by ADAC Ultra2 S466.
Consistency Check
In RAID, check consistency verifies the correctness of redundant data in an array. For example, in a system with dedicated parity, checking consistency means computing the parity of the data drives and comparing the results to the contents of the dedicated parity drive.
Fault Tolerance
Fault tolerance is achieved through cooling fans, power supplies, and the ability to hot swap drives. ADAC Ultra2 S466 provides hot swapping through the hot spare feature. A hot spare drive is an unused online available drive that ADAC Ultra2 S466 instantly plugs into the system when an active drive fails.
After the hot spare is automatically moved into the RAID subsystem, the failed drive is automatically rebuilt. The RAID disk array continues to handle request while the rebuild occurs.
8 ADAC Ultra2 S466 Hardware Guide
Disk Striping
Disk striping writes data across multiple disk drives instead of just one disk drive. Disk striping involves partitioning each drive storage space into stripes that can vary in size from 2 KB to 128 KB. These stripes are interleaved in a repeated sequential manner. The combined storage space is composed of stripes from each drive. ADAC Ultra2 S466 supports stripe sizes of 2 KB, 4 KB, 8 KB, 16 KB, 32 KB, 64 KB, or 128 KB.
For example, in a four-disk system using only disk striping (as in RAID level 0), segment 1 is written to disk 1, segment 2 is written to disk 2, and so on. Disk striping enhances performance because multiple drives are accessed simultaneously; but disk striping does not provide data redundancy.
Stripe Width Stripe width is the number of disks involved in an array where striping is implemented. For example, a four-disk array with disk striping has a stripe width of four.
Stripe Size The stripe size is the length of the interleaved data segments that ADAC Ultra2 S466 writes across multiple drives. ADAC Ultra2 S466 supports stripe sizes of 2 KB, 4 KB, 8 KB, 16 KB, 32 KB, 64 KB, or 128 KB.
Chapter 2 Introduction to RAID |
9 |
Disk Spanning
Disk spanning allows multiple disk drives to function like one big drive. Spanning overcomes lack of disk space and simplifies storage management by combining existing resources or adding relatively inexpensive resources. For example, four 400 MB disk drives can be combined to appear to the operating system as one single 1600 MB drive.
Spanning alone does not provide reliability or performance enhancements. Spanned logical drives must have the same stripe size and must be contiguous. In the following graphic, RAID 1 array is turned into a RAID 10 array.
Spanning for RAID 10, RAID 30, or RAID 50
Level |
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Description |
10Configure RAID 10 by spanning two contiguous RAID 1 logical drives. The RAID 1 logical drives must have the same stripe size.
30Configure RAID 30 by spanning two contiguous RAID 3 logical drives. The RAID 3 logical drives must have the same stripe size.
50Configure RAID 50 by spanning two contiguous RAID 5 logical drives. The RAID 5 logical drives must have the same stripe size.
Note: Spanning two contiguous RAID 0 logical drives does not produce a new RAID level or add fault tolerance. It does increase the size of the logical volume and improves performance by doubling the number of spindles.
10 ADAC Ultra2 S466 Hardware Guide
Disk Mirroring
With mirroring (used in RAID 1), data written to one disk drive is simultaneously written to another disk drive. If one disk drive fails, the contents of the other disk drive can be used to run the system and reconstruct the failed drive. The primary advantage of disk mirroring is that it provides 100% data redundancy. Since the contents of the disk drive are completely written to a second drive, it does not matter if one of the drives fails. Both drives contain the same data at all times. Either drive can act as the operational drive.
Disk mirroring provides 100% redundancy, but is expensive because each drive in the system must be duplicated.
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Chapter 2 Introduction to RAID |
11 |
||||||||||||||||||||||
Parity
Parity generates a set of redundancy data from two or more parent data sets. The redundancy data can be used to reconstruct one of the parent data sets. Parity data does not fully duplicate the parent data sets. In RAID, this method is applied to entire drives or stripes across all disk drives in an array. The types of parity are:
Type
Dedicated Parity
Distributed
Parity
Description
The parity of the data on two or more disk drives is stored on an additional disk.
The parity data is distributed across all drives in the system.
If a single disk drive fails, it can be rebuilt from the parity and the data on the remaining drives.
RAID level 3 combines dedicated parity with disk striping. The parity disk in RAID 3 is the last logical drive in a RAID set.
RAID level 5 combines distributed parity with disk striping. Parity provides redundancy for one drive failure without duplicating the contents of entire disk drives, but parity generation can slow the write process. A dedicated parity scheme during normal read/write operations is shown below:
12 ADAC Ultra2 S466 Hardware Guide
Hot Spares
A hot spare is an extra, unused disk drive that is part of the disk subsystem. It is usually in standby mode, ready for service if a drive fails. Hot spares permit you to replace failed drives without system shutdown or user intervention.
ADAC Ultra2 S466 implements automatic and transparent rebuilds using hot spare drives, providing a high degree of fault tolerance and zero downtime. The ADAC Ultra2 S466 RAID Management software allows you to specify physical drives as hot spares. When a hot spare is needed, the ADAC Ultra2 S466 controller assigns the hot spare that has a capacity closest to and at least as great as that of the failed drive to take the place of the failed drive.
Important
Hot spares are only employed in arrays with redundancy, for example, RAID levels 1, 3, 5, 10, 30, and 50.
A hot spare connected to a specific ADAC Ultra2 S466 controller can only be used to rebuild a drive that is connected to the same controller.
Chapter 2 Introduction to RAID |
13 |
Disk Rebuild
You rebuild a disk drive by recreating the data that had been stored on the drive before the drive failed.
Rebuilding can be done only in arrays with data redundancy such as RAID level 1, 3, 5, 10, 30, and 50.
Standby (warm spare) rebuild is employed in a mirrored (RAID 1) system. If a disk drive fails, an identical drive is immediately available. The primary data source disk drive is the original disk drive.
A hot spare can be used to rebuild disk drives in RAID 1, 3, 5, 10, 30, or 50 systems. If a hot spare is not available, the failed disk drive must be replaced with a new disk drive so that the data on the failed drive can be rebuilt.
The ADAC Ultra2 S466 controller automatically and transparently rebuilds failed drives with user-definable rebuild rates. If a hot spare is available, the rebuild starts automatically when a drive fails. ADAC Ultra2 S466 automatically restarts the system and the rebuild if the system goes down during a rebuild.
Rebuild Rate The rebuild rate is the fraction of the compute cycles dedicated to rebuilding failed drives. A rebuild rate of 100 percent means the system is totally dedicated to rebuilding the failed drive.
The ADAC Ultra2 S466 rebuild rate can be configured between 0% and 100%. At 0%, the rebuild is only done if the system is not doing anything else. At 100%, the rebuild has a higher priority than any other system activity.
Physical Array A RAID array is a collection of physical disk drives governed by the RAID management software. A RAID array appears to the host computer as one or more logical drives.
14 ADAC Ultra2 S466 Hardware Guide
Logical Drive
A logical drive is a partition in a physical array of disks that is made up of contiguous data segments on the physical disks. A logical drive can consist of any of the following:
∙an entire physical array,
∙more than one entire physical array,
∙a part of an array,
∙parts of more than one array, or
∙a combination of any two of the above conditions.
Hot Swap
A hot swap is the manual replacement of a defective physical disk unit while the computer is still running. When a new drive has been installed, you must issue a command to rebuild the drive.
Chapter 2 Introduction to RAID |
15 |
SCSI Drive States
State
Online (ONLIN)
Ready (READY)
Hot Spare
(HOTSP)
Fail (FAIL)
Rebuild
(REB)
A SCSI disk drive can be in one of these states:
Description
The drive is functioning normally and is a part of a configured logical drive.
The drive is functioning normally but is not part of a configured logical drive and is not designated as a hot spare.
The drive is powered up and ready for use as a spare in case an online drive fails.
A fault has occurred in the drive placing it out of service.
The drive is being rebuilt with data from a failed drive.
Logical Drive States
State |
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Description |
Optimal |
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The drive operating condition is good. All configured drives are |
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online |
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Degraded |
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The drive operating condition is not optimal. One of the |
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configured drives has failed or is offline. |
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Failed |
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The drive has failed. |
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Offline |
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The drive is not available to ADAC Ultra2 S466. |
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16 ADAC Ultra2 S466 Hardware Guide
Disk Array Types
Type
Software-
Based
SCSI to SCSI
Bus-Based
The RAID disk array types are:
Description
The array is managed by software running in a host computer using the host CPU bandwidth. The disadvantages associated with this method are the load on the host CPU and the need for different software for each operating system.
The array controller resides outside of the host computer and communicates with the host through a SCSI adapter in the host. The array management software runs in the controller. It is transparent to the host and independent of the host operating system. The disadvantage is the limited data transfer rate of the SCSI channel between the SCSI adapter and the array controller.
The array controller resides on the bus (for example, a PCI or EISA bus) in the host computer and has its own CPU to generate the parity and handle other RAID functions. A bus-based controller can transfer data at the speed of the host bus (PCI, ISA, EISA, VLBus) but is limited to the bus it is designed for. ADAC Ultra2 S466 resides on a PCI bus, which can handle data transfer at up to 132 MB/s. With ADAC Ultra2 S466, the channel can handle data transfer rates up to 80 MB/s per SCSI channel.
Enclosure Management
Enclosure management is the intelligent monitoring of the disk subsystem by software and/or hardware.
The disk subsystem can be part of the host computer or separate from it. Enclosure management helps you stay informed of events in the disk subsystem, such as a drive or power supply failure. Enclosure management increases the fault tolerance of the disk subsystem.
Chapter 2 Introduction to RAID |
17 |
18 ADAC Ultra2 S466 Hardware Guide
3 RAID Levels
There are six official RAID levels (RAID 0 through RAID 5). ADAC Ultra2 S466 supports RAID levels 0, 1, 3, and 5. Gateway has designed three additional RAID levels (10, 30, and 50) that provide additional benefits. The RAID levels that ADAC Ultra2 S466 supports are:
RAID Level |
Type |
turn to |
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0 |
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Standard |
page 21 |
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1 |
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Standard |
page 22 |
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3 |
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Standard |
page 23 |
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5 |
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Standard |
page 25 |
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10 |
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ADAC Ultra2 S466 only |
page 26 |
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30 |
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ADAC Ultra2 S466 only |
page 27 |
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50 |
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ADAC Ultra2 S466 only |
page 28 |
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Select RAID Level To ensure the best performance, you should select the optimal RAID level when you create a system drive. The optimal RAID level for your disk array depends on a number of factors:
∙the number of drives in the disk array,
∙the capacity of the drives in the array,
∙the need for data redundancy, and
∙the disk performance requirements.
Selecting a RAID Level The factors you need to consider when selecting a RAID level are listed on the next page
Chapter 3 RAID Levels |
19 |
Selecting a RAID Level
Level |
Description and |
Pros |
Cons |
Max. |
Fault |
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Use |
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Drives |
Tolerant |
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0 |
Data divided in |
High data |
No fault |
One to |
No |
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blocks and |
throughput |
tolerance. All |
32 |
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distributed |
for large |
data lost if |
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sequentially (pure |
files |
any drive |
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striping). Use for |
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fails. |
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non-critical data |
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that requires high |
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performance. |
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1 |
Data duplicated on |
100% data |
Doubles disk |
2, 4, 6, |
Yes |
||
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another disk |
redundancy |
space. |
or 8 |
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(mirroring). Use |
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Reduced |
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for read-intensive |
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performance |
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fault-tolerant |
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during |
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systems |
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rebuilds. |
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3 |
Disk striping with a |
Achieves |
Performance |
Three to |
Yes |
||
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dedicated parity |
data |
not as good as |
eight |
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drive. Use for non- |
redundancy |
RAID 1 |
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interactive apps |
at low cost |
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that process large |
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files sequentially. |
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5 |
Disk striping and |
Achieves |
Performance |
Three to |
Yes |
||
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parity data across |
data |
not as good as |
eight |
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all drives. Use for |
redundancy |
RAID 1 |
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high read volume |
at low cost |
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but low write |
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volume, such as |
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transaction |
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processing. |
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10 |
Data striping and |
High data |
More |
4, 6, or |
Yes |
||
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mirrored drives. |
transfers, |
complicated |
8 |
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complete |
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redundancy |
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30 |
Disk striping with a |
High data |
More |
Six to |
Yes |
||
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dedicated parity |
transfers, |
complicated |
32 |
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drive. |
redundancy |
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50 |
Disk striping and |
High data |
More |
Six to |
Yes |
||
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parity data across |
transfers, |
complicated |
32 |
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all drives. |
redundancy |
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20 ADAC Ultra2 S466 Hardware Guide