Apple XSAN 1.1 Administrator Guide

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Apple XSAN 1.1 Administrator Guide

Xsan

Administrator’s Guide

Information for setting up and managing Xsan volumes in a storage area network using Xsan Admin or the command line

For Xsan 1.1

K Apple Computer, Inc.

© 2005 Apple Computer, Inc. All rights reserved.

Under the copyright laws, this manual may not be copied, in whole or in part, without the written consent of Apple.

The Apple logo is a trademark of Apple Computer, Inc., registered in the U.S. and other countries. Use of the “keyboard” Apple logo (Option-Shift-K) for commercial purposes without the prior written consent of Apple may constitute trademark infringement and unfair competition in violation of federal and state laws.

Every effort has been made to ensure that the information in this manual is accurate. Apple is not responsible for printing or clerical errors.

Apple

1 Infinite Loop

Cupertino, CA 95014-2084 408-996-1010 www.apple.com

Apple, the Apple logo, Final Cut Pro, Mac, Macintosh, the Mac logo, Mac OS, Power Mac, and Xserve are trademarks of Apple Computer, Inc., registered in the U.S. and other countries.

Finder and Xsan are trademarks of Apple Computer, Inc.

StorNext and ADIC are registered trademarks of Advanced Digital Information Corporation.

Other company and product names mentioned herein are trademarks of their respective companies. Mention of third-party products is for informational purposes only and constitutes neither an endorsement nor a recommendation. Apple assumes no responsibility with regard to the performance or use of these products.

The product described in this manual incorporates copyright protection technology that is protected by method claims of certain U.S. patents and other intellectual property rights owned by Macrovision Corporation and other rights owners. Use of this copyright protection technology must be authorized by Macrovision Corporation and is intended for home and other limited viewing uses only unless otherwise authorized by Macrovision Corporation. Reverse engineering or disassembly is prohibited.

Apparatus Claims of U.S. Patent Nos. 4,631,603, 4,577,216, 4,819,098 and 4,907,093 licensed for limited viewing uses only.

Simultaneously published in the United States and Canada.

034-3114-A/05-30-05

Contents

Preface

9

About This Guide

 

10

What’s New in Xsan 1.1

 

11

Version Compatibility

 

11

Upgrading From an Earlier Version of Xsan

 

12

Notation Conventions

Chapter 1

13

Overview of Xsan

 

13

What Is Xsan?

 

14

Xsan Storage Area Networks

 

15

Shared SAN Volumes

 

15

Controllers and Clients

 

15

SAN Connections

 

16

How Xsan Storage Is Organized

 

16

LUNs (RAID Arrays)

 

17

Storage Pools

 

17

Volumes

 

18

Folders With Affinities

 

19

How Xsan Utilizes Available Storage

 

19

Metadata and Journal Data

 

19

Striping at a Higher Level

 

19

Security

 

20

Expanding Storage

 

20

Xsan Capacities

Chapter 2

21

Setting Up a Storage Area Network

 

21

Hardware and Software Requirements

 

21

Supported Computers

 

22

Supported Storage Devices

 

22

Fibre Channel Fabric

 

23

Ethernet TCP/IP Network

 

23

Directory Services

 

24

Outgoing Mail Service

 

25

Planning Your SAN

3

26 Planning Considerations and Guidelines

31Connecting Computers and Storage Devices

31Preparing LUNs (RAID Arrays and Slices)

32Using the Xsan Admin Application

32Installing Xsan Admin Separately

32Connecting Through a Firewall

32Xsan Admin Preferences

32Getting Help

32Using the Command Line

33SAN and Volume Setup Summary

34Setting Up an Xsan Volume on a Storage Area Network

48Renaming a SAN

48Deleting a SAN

49Setting Up Additional SANs

Chapter 3

51

Managing SAN Storage

 

52

Adding Storage

 

52

Restoring the Previous Volume Configuration After Changes

 

52

About Rearranging Fibre Channel Connections

 

53

Adding LUNs to a Storage Pool

 

55

Adding a Storage Pool to a Volume

 

56

Adding a Volume to a SAN

 

57

Assigning a Storage Pool Affinity to a Folder

 

58

Assigning an Affinity to a Folder Within a Folder

 

59

Removing an Affinity

 

60

Changing Storage Pool Settings

 

61

Renaming a Storage Pool

 

61

Choosing the Types of Files Stored on a Storage Pool

 

62

Setting Storage Pool Stripe Breadth

 

63

Setting Storage Pool Access Permissions

 

63

Setting the Selection Method for Multiple Connections

 

64

Changing Volume Settings

 

65

Renaming a Volume

 

66

Setting the Block Allocation Size

 

67

Setting the Volume Allocation Strategy

 

67

Checking Volume Fragmentation

 

68

Defragmenting a Volume

 

68

Checking the Integrity of a Volume

 

69

Repairing a Volume

Chapter 4

71

Managing Clients and Users

 

72

Adding a Client

 

73

Adding a Client to a StorNext SAN

4

Contents

 

 

73Mounting a Volume on a Client

74Controlling Client and User Access

74Controlling Access to Folders on Volumes

74Unmounting a Volume on a Client

74Restricting a Client to Read-Only Access

75Removing a Client From a SAN

75Removing Xsan Software From a Computer

76Setting User and Group Quotas

77About Xsan Quotas

78Checking User Quota Use

79Helping Clients Check Their Own Quotas

79 Creating Local Home Directories for Network Accounts

Chapter 5

81

Managing Metadata Controllers

 

82

Adding a Controller

 

83

Setting Controller Failover Priority

 

83

Switching to a Standby Controller

 

84

Finding Out Which Controller Is Hosting a Volume

 

85

Listing the Volumes Hosted by a Controller

 

86

Changing a Controller’s IP Address

 

87

Upgrading Controller Software

 

87

Monitoring Controller Status

Chapter 6

89

Monitoring SAN Status

 

90

Locking Xsan Admin Views for Secure Monitoring

 

90

Checking Overall SAN Status

 

91

Checking Overall Volume Status

 

92

Checking Free Space on a Volume

 

92

Checking Free Space on a Storage Pool

 

92

Checking Quota Use

 

93

Viewing a Controller’s CPU and Network Utilization

 

93

Viewing File System CPU and Memory Utilization

 

94

Setting Up Status Notifications

 

94

Checking the Status of File System Processes

 

95

Viewing Xsan Logs

 

95

Checking Volume Clients

 

96

Checking for Fibre Channel Connection Failures

 

96

Checking the State of Xserve RAID Systems

Chapter 7

97

Solving SAN Problems

 

97

You’re Unable to Install the Xsan Software

 

97

Some Computers Aren’t Listed in Xsan Admin

 

97

You’re Unable to Connect to a Computer Using Xsan Admin

Contents

5

 

 

97You’re Unable to Mount a Volume on a Client

98Xserve RAID LUNs Aren’t Accessible Over Fibre Channel

98You’re Unable to Add a Storage Pool

99Some LUNs Aren’t Listed in Xsan Admin

99 Some LUNs Are Listed Twice in Xsan Admin

100Problems Using Command-Line Tools

100A Client User Sees Error Code –1425

100A LUN Doesn’t Have as Much Space as Expected

100Files and Folders Created by Mac OS 9 Computers Show the Wrong Creation Date

101You’re Unable to Rename an Xsan Volume in the Finder

101You’re Unable to Restart a Volume After Adding LUNs or Storage Pools

101Fibre Channel Performance Is Poorer Than Expected

101You’re Unable to Add LUNs to a Storage Pool

102A Client is Unable to Use a Volume After a Fibre Channel Interruption

102SAN Performance Declines Periodically and Predictably

Appendix A

103

Combining Xsan and StorNext Clients and Controllers

 

103

Compatible Software Versions

 

104

Licensing

 

104

Terminology

 

105

Adding Macintosh Clients to a StorNext SAN

 

106

Using Xsan Controllers With StorNext Clients

Appendix B

107

Using the Command Line

 

107

Using the Shell Commands

 

107

Sending Commands to Remote Computers

 

107

Viewing the Man Pages

 

108

Notation Conventions

 

108

The Commands

 

109

Viewing or Changing Volume and Storage Pool Settings (cvadmin)

 

112

Copying Files or Folders (cvcp)

 

113

Checking or Repairing a Volume (cvfsck)

 

114

Labeling, Listing, and Unlabeling LUNs (cvlabel)

 

114

Creating a Folder With an Affinity (cvmkdir)

 

115

Creating and Pre-Allocating a File (cvmkfile)

 

116

Initializing a Volume (cvmkfs)

 

116

Applying Volume Configuration Changes (cvupdatefs)

 

116

Starting a Volume Controller (fsm)

 

117

Starting a Port Mapper Process (fsmpm)

 

117

Defragmenting a File, Directory, or Volume (snfsdefrag)

 

119

Mounting an Xsan Volume

 

119

Unmounting an Xsan Volume

 

119

Viewing Logs

6

Contents

 

 

120 The Configuration Files

120 The Volume Configuration File

123 Additional Examples

123 The Volume Auto-Start List

125 The Controller List

Glossary 127

Index 131

Contents

7

 

 

About This Guide

Preface

Use this guide to learn how to set up and manage Xsan volumes on a storage area network.

This guide shows how to use Xsan to combine Xserve RAID arrays and slices into large, easy-to-expand volumes of storage that clients use like local disks but are actually shared over a high-speed Fibre Channel fabric.

Chapter 1 provides an overview of Xsan and how you can use it to organize RAID arrays into shared volumes of storage.

Chapter 2 includes hardware and software requirements, SAN planning guidelines, and basic steps for setting up an Xsan volume.

Chapter 3 contains instructions for expanding storage, creating folders with affinities, changing volume and storage pool settings, and checking, defragmenting, and repairing SAN volumes.

Chapter 4 shows how to add client computers to a SAN, mount volumes on clients, control client and user access to SAN files, and control user space using quotas.

Chapter 5 contains information on managing volume metadata controllers.

Chapter 6 includes instructions for monitoring and automatically reporting the condition of a SAN.

Chapter 7 lists solutions to common problems you might encounter.

Appendix A contains information to help you combine Xsan controllers or clients with ADIC StorNext controllers or clients in the same SAN.

Appendix B describes command-line utilities and configuration files you can use to manage an Xsan SAN using Terminal.

9

What’s New in Xsan 1.1

When you run the Xsan installer it installs either Xsan 1.1 for Mac OS X v10.3 or Xsan 1.1 for Mac OS X v10.4 to match the operating system of the target computer. Xsan 1.1 offers these new features and capabilities:

ÂYou can use the new Lock View command in Xsan Admin to monitor a SAN from an unsecured computer without the risk of a passerby mounting, unmounting, starting, or stopping volumes or otherwise changing the SAN configuration.

ÂYou can have Xsan Admin send an email notification to warn you if the Xsan software serial number on a controller or client is about to expire.

ÂYou can purchase and use site-licensed serial numbers.

ÂYou can take advantage of both block-level and byte-level locking.

ÂYou can use the Xsan User Quotas application to check user quotas from a client without using Xsan Admin.

Â(Mac OS X version 10.4 only) You can create files and volumes as large as 1024 terabytes (TB).

10

Preface About This Guide

 

 

Version Compatibility

The following table shows which versions of Xsan and StorNext controllers and clients can be used in the same SAN.

Controller

Client

Compatible?

Xsan 1.0.x or 1.1 (Mac OS X v10.3)

Xsan 1.0.x or 1.1 (Mac OS X v10.3)

Yes

 

 

 

 

Xsan 1.1 (Mac OS X v10.4))

No

 

 

 

 

StorNext 2.4

Yes

 

 

 

 

StorNext 2.5

No

 

 

 

Xsan 1.1 (Mac OS X v10.4)

Xsan 1.0.x or 1.1 (Mac OS X v10.3)

Yes

 

 

 

 

Xsan 1.1 (Mac OS X v10.4)

Yes

 

 

 

 

StorNext 2.4

No

 

 

 

 

StorNext 2.5

Yes

 

 

 

StorNext 2.4

Xsan 1.0.x or 1.1 (Mac OS X v10.3)

Yes

 

 

 

 

Xsan 1.1 (Mac OS X v10.4)

No

 

 

 

 

StorNext 2.4

Yes

 

 

 

 

StorNext 2.5

No

 

 

 

StorNext 2.5

Xsan 1.0.x or 1.1 (Mac OS X v10.3)

Yes

 

 

 

 

Xsan 1.1 (Mac OS X v10.4)

Yes

 

 

 

 

StorNext 2.4

Yes

 

 

 

 

StorNext 2.5

Yes

 

 

 

Important: Note that if any client on your SAN is running Xsan 1.1 on Mac OS X v10.4, your controllers must all be running the same (Xsan 1.1 on Mac OS X v10.4). You can’t use a controller running Mac OS X v10.3 if any client is running Xsan 1.1 on Mac OS X v10.4.

Upgrading From an Earlier Version of Xsan

For more information on migrating your SAN storage to Xsan 1.1 from an earlier version of Xsan, including tips for upgrading with the least impact on existing storage, see the Xsan Migration Guide at www.apple.com/server/documentation.

Preface About This Guide

11

 

 

Notation Conventions

The following conventions are used in this book wherever shell commands or other command-line items are described.

Notation

Indicates

monospaced font

A command or other terminal text

 

 

$

A shell prompt

 

 

[text_in_brackets]

An optional parameter

 

 

(one|other)

Alternative parameters (type one or the other)

 

 

underlined

A parameter you must replace with a value

 

 

[...]

A parameter that may be repeated

 

 

<anglebrackets>

A displayed value that depends on your SAN configuration

 

 

12

Preface About This Guide

 

 

Overview of Xsan

1

 

 

 

This chapter gives you an overview of Xsan and storage area networks.

Read this chapter for an overview of Xsan and how you can use it to set up a storage area network (SAN) to provide fast, shared storage.

What Is Xsan?

Xsan is a storage area network file system and a management application (Xsan Admin) that you can use to provide users or applications on client computers with shared highspeed access to expandable storage.

Fibre

Storage

Channel

pools

RAID

arrays (LUNs)

13

Xsan Storage Area Networks

A storage area network is a way of connecting computers to storage devices that gives users very fast access to files and gives administrators the ability to expand storage capacity as needed without interrupting users.

An Xsan SAN consists of:

ÂVolumes of shared storage, stored on Xserve RAID systems, available to clients as mounted volumes that they can use like local disks

ÂAt least one computer acting as a metadata controller that coordinates access to the shared volumes

ÂClient computers that access storage in accordance with established permissions and quotas

ÂUnderlying Fibre Channel and Ethernet networks

The following illustration shows the physical components of a typical Xsan SAN.

Metadata

Standby

controller

controller

Clients

Fibre

Channel switch

Xserve RAID storage

Ethernet - TCP/IP

(Private)

Ethernet - TCP/IP

Intranet/

(Public)

Internet

14

Chapter 1 Overview of Xsan

 

 

Shared SAN Volumes

Users and applications see shared SAN storage as local volumes. Xsan volumes are logical disks made up of groups of RAID arrays. The elements you combine to create an Xsan volume are described under “How Xsan Storage Is Organized” on page 16.

Controllers and Clients

When you add a computer to an Xsan SAN, you specify whether it will play the role of client, controller, or both.

Controllers

When you set up an Xsan SAN, you assign at least one computer to act as the controller. The controller manages the SAN volume metadata, maintains a file system journal, and controls concurrent access to files. Metadata includes such information as where files are actually stored and what portions of available storage are allocated to new files.

For high availability, you can add more than one controller to a SAN, as shown in the illustration on page 14. If the primary controller fails, the standby controller takes over. Controllers can also act as clients, so you can use a standby controller as a working client while the primary controller is operational.

Clients

The computers that users or applications use to access SAN volumes are called clients. Clients communicate with controllers over the Ethernet network but use Fibre Channel to send and retrieve file data to and from the RAID systems that provide storage for the volumes.

SAN Connections

Xsan uses independent networks to connect storage devices, metadata controllers, and client computers: a Fibre Channel network and one or two Ethernet networks.

User Data Over Fibre Channel

User data is transferred over high-speed Fibre Channel connections. Controllers also use a Fibre Channel connection to move metadata to and from the volume.

Metadata Over Ethernet

To eliminate unnecessary traffic on the Fibre Channel connections, controllers and clients use an Ethernet network to exchange file system metadata. (When a controller reads or writes metadata on a volume, it uses Fibre Channel.) The Xsan Admin application also uses the Ethernet connection to let you manage the SAN.

To prevent Internet or intranet traffic from interfering with metadata communications, you can set up separate Ethernet networks as shown in the illustration.

Chapter 1 Overview of Xsan

15

 

 

Fibre Channel Multipathing

Xsan can take advantage of multiple Fibre Channel connections between clients and storage. Xsan can alternate between connections for each read and write, or assign each LUN in a volume to one of the connections when the volume is mounted.

How Xsan Storage Is Organized

Users use an Xsan volume the same way they use a local disk. What they don’t see is that the SAN volume actually consists of numerous physical disks combined on several levels using RAID techniques.

The following illustration shows an example of how disk space provided by the individual drive modules in Xserve RAID systems is combined into a volume that users see as a large local disk.

Shared SAN

volume

Faster

Affinity

Safer

Affinity

 

 

 

 

 

 

 

Storage pool

 

 

 

 

 

 

 

 

 

 

 

 

 

Storage pool

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Striping)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Striping)

 

 

 

 

 

 

 

 

LUN

 

 

 

LUN

 

 

 

 

LUN

 

 

 

LUN

 

 

 

 

LUN

 

 

 

LUN

 

 

 

 

LUN

 

 

 

LUN

 

 

RAID 0

 

 

RAID 0

 

 

 

RAID 0

 

 

RAID 0

 

 

 

RAID 5

 

 

RAID 5

 

 

 

RAID 5

 

 

RAID 5

 

 

 

array

 

 

array

 

 

 

 

array

 

 

array

 

 

 

 

array

 

 

array

 

 

 

 

array

 

 

array

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The following paragraphs describe these storage elements and how you organize them to create shared Xsan volumes.

LUNs (RAID Arrays)

The smallest storage element you work with in Xsan is a logical storage device called a LUN (a SCSI logical unit number). In most storage area networks a LUN represents a group of drives such as a RAID array or a JBOD (just a bunch of disks) device. In Xsan, LUNs are Xserve RAID arrays or slices.

16

Chapter 1 Overview of Xsan

 

 

You create a LUN when you use RAID Admin to create an Xserve RAID array. The controller hardware and software in the Xserve RAID system combine individual drive modules into an array based on the RAID scheme you choose. Each array appears on the network as a separate LUN. If you slice an array, each slice appears as a LUN.

One of your first tasks when you set up a SAN volume is to prepare LUNs. If the two RAID 5 arrays on a new Xserve RAID are not right for your application, you can use RAID Admin to create arrays based on other RAID schemes. For help choosing schemes for your LUNs, see “Choosing RAID Schemes for LUNs” on page 28.

The illustration on page 16 shows four Xserve RAID systems hosting two arrays each. Half of the arrays use a RAID 0 scheme (striping only) for speed while the others use RAID 5 (distributed parity) to ensure against data loss. Xsan sees the arrays as LUNs that can be combined to create a volume.

After your Xserve RAID LUNs are set up, you label and initialize them for use with the Xsan file system using Xsan Admin.

Storage Pools

LUNs are combined to form storage pools. A storage pool in a small volume might consist of a single RAID array, but storage pools in many volumes consist of multiple arrays.

Xsan distributes file data in parallel across the LUNs in a storage pool using a RAID 0 (striping) scheme. So, you can improve a client’s access speed by distributing available storage over several LUNs in a storage pool.

You can set up storage pools that have different performance or recoverability characteristics and assign folders to them using affinities. Users can then select where to store files based on their need for speed or safety. See “Folders With Affinities” on page 18.

As an example, the illustration on page 16 shows eight LUNs combined into two storage pools, one pool consisting of RAID 0 (fast but not recoverable) arrays and the other made up of RAID 5 (not as fast, but recoverable) arrays. Xsan stripes data across the four LUNs in each storage pool.

You use Xsan Admin to add available LUNs to specific storage pools.

Volumes

Storage pools are combined to create the volumes that users see. From the user’s perspective, the SAN volume looks and behaves just like a large local disk, except that:

ÂThe size of the volume can grow as you add underlying arrays or storage pools

ÂOther users on the SAN can access files on the volume at the same time

Chapter 1 Overview of Xsan

17

 

 

In the example illustrated on page 16, two storage pools are combined to create a single shared volume.

You create volumes and mount them on client computers using the Xsan Admin application.

The following screen image shows how LUNs, storage pools, and volumes appear as you organize them in the Xsan Admin application. This example shows a SAN named “Editing SAN” with a single shared volume named “SanVol.” Storage for the volume is provided by two storage pools,“Meta” and “Data,” the first based on a single LUN and the second on two. Each of the LUNs is a 3-disk RAID 5 array on an Xserve RAID using 115 GB drive modules.

SAN

Volume

Storage pool

LUN

Folders With Affinities

To control which storage pool is used to store specific files (for example, to provide different levels of service for different users or applications), you can associate a folder on an Xsan volume with one of the storage pools that make up the volume.

If, for example, you set up storage pools with different balances of performance and data redundancy, users can choose between faster and safer storage by putting files in the appropriate folder.

18

Chapter 1 Overview of Xsan

 

 

In the illustration on page 16, a predefined folder has an affinity for the faster storage pool that is based on RAID 0 arrays. Any file that a user copies into this folder is automatically stored on the faster arrays. A second folder is associated with the more secure RAID 5 storage.

How Xsan Utilizes Available Storage

Xsan stores both user files and file system data on SAN volumes, and stripes data across the LUNs in a volume for better performance.

Metadata and Journal Data

Xsan records information about the files in an Xsan volume using metadata files and file system journals. File system metadata includes information such as which specific parts of which disks are used to store a particular file and whether the file is being accessed. The journal data includes a record of file system transactions that can help ensure the integrity of files in the event of a failure.

These files are managed by the Xsan metadata controller, but are stored on SAN volumes, not on the controller itself. By default, metadata and journal data are stored on the first storage pool you add to a volume. You can use Xsan Admin to choose where these files are stored when you add storage pools to a new volume.

Striping at a Higher Level

When you write a file to a RAID array using RAID 0 (striping), the file is broken into segments that are spread across the individual disk drives in the array. This improves performance by writing pieces of the file in parallel (instead of one piece at a time) to the individual disks in the array. Xsan applies this same technique at a second, higher level in the storage hierarchy. Within each storage pool in a volume, Xsan stripes file data across the individual LUNs that make up the storage pool. Once again, performance is improved because data is written in parallel.

You can tune SAN performance by adjusting the amount of data written to each LUN in a storage pool (the “stripe breadth”) to suit a critical application.

Security

As SAN administrator, you can control access to shared volumes in several ways.

First, users cannot browse or mount SAN volumes. Only a SAN administrator can specify which volumes are mounted on which client computers. One way you can control access to data is to mount a volume only on appropriate client computers.

To prevent users from modifying data on a volume, you can mount the volume with read-only access.

Chapter 1 Overview of Xsan

19

 

 

You can also control user access to folders on a volume by specifying owner, group, and general access permissions as you would in the Finder.

You can also set up zones in the underlying Fibre Channel network to segregate users and volumes.

Expanding Storage

There are two ways you can add free space to an Xsan volume:

ÂAdd Xserve RAID systems (new LUNs) to existing storage pools

ÂAdd entire new storage pools to volumes

Both methods require you to unmount and remount the volume on clients.

You can also add new volumes to a SAN at any time.

For information on expanding Xsan storage, see “Adding Storage” on page 52.

Xsan Capacities

The following table lists limits and capacities for Xsan volumes.

Parameter

Maximum

Number of computers in a SAN (controllers and clients)

64

 

 

Number of storage pools in a volume

512

 

 

Number of LUNs in a storage pool

32

 

 

Number of LUNs in a volume

512

 

 

Number of files in a volume

4,294,967,296

 

 

LUN size

2 TB

 

 

Volume size

16 TB (Mac OS X v10.3)

 

1024 TB (Mac OS X v10.4)

 

 

File size

16 TB (Mac OS X v10.3)

 

1024 TB (Mac OS X v10.4)

 

 

Volume name length

70 characters

 

 

File or folder name length

251 characters

 

 

SAN name length

255 characters

 

 

Storage pool name length

255 characters

 

 

LUN name (label or disk name)

242 characters

 

 

20

Chapter 1 Overview of Xsan

 

 

Setting Up a Storage Area

2

Network

This chapter lists requirements, suggests planning tips, and gives instructions for setting up an Xsan SAN.

This chapter contains:

ÂXsan hardware and software requirements (page 21)

ÂPlanning guidelines (page 25)

ÂSAN setup instructions (page 33)

Hardware and Software Requirements

Your SAN environment needs to satisfy requirements in these areas:

ÂSupported computers

ÂSupported storage devices

ÂFibre Channel fabric, adapters, and switches

ÂEthernet network

ÂDirectory services (optional)

ÂOutgoing mail service (optional)

Supported Computers

Xsan controller and client computers must meet these minimum requirements:

Systems

ÂXserve

ÂXserve G5

ÂPower Mac G4 dual 800 MHz or faster

ÂPower Mac G5

Memory

ÂClients should have a minimum of 256 MB of RAM.

ÂControllers should have a minimum of 512 MB of RAM. For optimum performance, add an additional 512 MB of RAM for each SAN volume hosted by the controller.

21

Supported Operating Systems

ÂMac OS X or Mac OS X Server v.10.3.9 (Xsan 1.1 for Mac OS X v10.3)

ÂMac OS X or Mac OS X Server v10.4 or later (Xsan 1.1 for Mac OS X v10.4)

Windows, AIX, IRIX, Linux, and Solaris clients must be running ADIC’s StorNext File

System version 2.4 or 2.5. For complete compatibility information, see “Version

Compatibility” on page 11.

Supported Storage Devices

Although you can use any standard LUN storage device, this guide assumes you are using Xserve RAID systems for your storage devices.

Important: Be sure to install the latest firmware update on your Xserve RAID systems before you use them with Xsan.

For demanding applications such as video editing, use Xserve RAID systems that have:

ÂA full set of 14 Apple Drive Modules

Â512 MB of cache in each controller (1 GB total)

Fibre Channel Fabric

Unlike file system metadata, which controllers and clients exchange over Ethernet, actual file content in an Xsan SAN is transferred over Fibre Channel connections (as is metadata that controllers access on a volume). To set up the connections, you need:

ÂApple Fibre Channel PCI or PCI-X cards for each client and controller computer

ÂOne or more supported Fibre Channel switches

ÂFibre Channel cables connecting computers and storage devices to the switches to form a Fibre Channel fabric

Fibre Channel PCI Cards

Install Apple Fibre Channel PCI or PCI-X cards in all Macintosh computers that will connect to the SAN.

Fibre Channel Switches

The following Fibre Channel switches have been tested with Xsan, Xserve RAID systems, and the Apple Fibre Channel PCI and PCI-X cards:

ÂBrocade Silkworm 3200, 3800, 3900, and 12000 series

ÂQLogic SANbox 2–8, SANbox 2–16, SANbox 2–64, and SANbox 5200

ÂEmulex SAN Switch 355, 375, and 9200

ÂCisco MDS 9000 family

For the latest additions to this list of qualified switches, see the Xsan webpages at

www.apple.com/xsan.

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Fabric Configuration

You must connect the computers, storage devices, and switches in your Fibre Channel network to form a Fibre Channel “fabric.” In a fabric, Fibre Channel cables connect node ports (F or N_Port). See the documentation that came with your Fibre Channel switches for more information.

Note: If you are using a Vixel 355 switch, you must connect Xserve RAID systems to an FL (arbitrated loop) port on the switch.

You cannot use Fibre Channel Arbitrated Loop (FL ports) with an Xsan SAN, with the exception noted above for Vixel 355 switches.

Ethernet TCP/IP Network

Computers in the SAN must also be connected to an Ethernet network. Xsan uses this network instead of the Fibre Channel network to transfer file system metadata, reserving the Fibre Channel connections for actual file contents.

If the computers in your SAN need to communicate with directory servers, a corporate or campus intranet, or the Internet, you should connect each SAN client and controller to two separate Ethernet networks: one private subnet for the SAN and a separate connection for directory, intranet, or Internet traffic. This is important if you plan to use the SAN for high-performance applications such as video editing.

IP Addresses and Domain Names

For best results, assign fixed, non-routed IP addresses to all clients, controllers, and storage devices connected to the SAN Ethernet network. You can use the following ranges of IP addresses in your private (non-routed) subnet:

Private address range

Associated subnet mask

Comments

10.0.0.0 – 10.255.255.255

255.0.0.0

10/8

 

 

 

172.16.0.0 – 172.31.255.255

255.240.0.0

172.16/12

 

 

 

192.168.0.0 – 192.168.255.255

255.255.0.0

192.168/16

 

 

 

Directory Services

If you plan to use user and group privileges to control access to files and folders on the SAN, you can simplify management by setting up or joining a user and group directory. Although not required, a central directory lets you manage users and groups on one computer instead of having to visit all SAN clients and controllers.

If you already have a directory, you can use the Directory Access application on each controller and client to access the directory for user and group information.

If you don’t use a central directory service, you need to set up users and groups on each SAN computer.

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Important: If you create users and groups on each SAN computer, be sure that 1) each user or group has a numeric user ID (UID) or group ID (GID) that is unique throughout the SAN and 2) each user or group defined on more than one computer has the same UID or GID on each computer.

If you don’t have access to a directory, you can use the directory services in Mac OS X Server to set up an LDAP directory of SAN users and groups.

Note: If you do create your user accounts in a centralized directory, be aware that some applications running on SAN client computers, such as Final Cut Pro, for example, work better when users have local home directories. For help setting up local home directories for users with network accounts, see “Creating Local Home Directories for Network Accounts” on page 79.

Outgoing Mail Service

Xsan can send SAN status notifications via email on your local subnet or corporate network without using a separate mail server. However, to send notifications outside your local network, you need an SMTP server to act as a mail gateway. If you don’t have access to an outgoing mail server, you can use the mail service in Mac OS X Server to set one up.

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Planning Your SAN

It’s easy to add storage to an existing Xsan SAN, but reorganizing a SAN after you set it up is not so simple. So, it’s important to plan the layout and organization of your SAN and its storage before you set it up.

An Xsan SAN is composed of:

ÂStorage devices (usually Xserve RAID systems)

ÂLUNs (logical unit numbers, usually RAID arrays)

ÂStorage pools (groups of LUNs)

ÂVolumes (groups of storage pools visible to users)

ÂClients (computers that use volumes)

ÂControllers (computers that manage volume metadata)

ÂUnderlying Fibre Channel and Ethernet networks

Before you use Xsan Admin to set up a SAN, decide how you want to organize these components. Take the time to create a drawing or a table that organizes available hardware into RAID arrays, storage pools, volumes, client computers, and controllers in a way that meets both your users’ needs and your needs as SAN administrator.

First, consider these questions:

ÂHow much storage do you need?

ÂHow do you want to present available storage to users?

ÂWhat storage organization makes the most sense for user workflow?

ÂWhat levels of performance do your users require?

ÂHow important is constant availability?

ÂWhat are your requirements for security?

Your answers to the above questions will help you decide the following:

ÂWhat RAID schemes should you use for your RAID arrays?

ÂHow many SAN volumes do you need?

ÂHow should individual volumes be organized?

ÂWhich LUNs go in each storage pool?

ÂWhich storage pools make up each volume?

ÂWhich clients, users, and groups should have access to each volume?

ÂWhich computers will act as controllers?

ÂDo you need standby controllers?

ÂDo you want to use controllers as clients also?

ÂWhere do you want to store file system metadata and journal data?

ÂWhat allocation strategy should you use?

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Review the considerations and guidelines on the following pages for help translating your answers into a suitable SAN design.

Planning Considerations and Guidelines

The following paragraphs might help you make some of your SAN design decisions.

How Much Storage?

Because it’s easy to add storage to an Xsan SAN, you only need to decide on an adequate starting point. You can then add storage for user data as needed.

You can’t expand a storage pool that is used to store volume metadata and journal data. For information on estimating your metadata and journal data storage requirements, see “Estimating Metadata and Journal Data Storage Needs” on page 31.

Note that the number of Xserve RAID systems you use affects not only available space but also SAN performance. See “Performance Considerations” below.

How Should Users See Available Storage?

If you want the users working on a particular project to see a volume dedicated to their work, create a separate volume for each project. If it’s acceptable for a user to see a folder for his or her work on a volume with others’ folders, you can create a single volume and organize it into project folders.

Workflow Considerations

How much file sharing is required by your users’ workflow? If, for example, different users or groups work on the same files, either simultaneously or in sequence, it makes sense to store those files on a single volume to avoid having to maintain or hand off copies. Xsan uses file locking to manage shared access to a single copy of the files.

Performance Considerations

If your SAN supports an application (such as high resolution video capture and playback) that requires the fastest possible sustained data transfers, design your SAN with these performance considerations in mind:

ÂSet up the LUNs (RAID arrays) using a RAID scheme that offers high performance. See “Choosing RAID Schemes for LUNs” on page 28.

ÂGroup your fastest LUNs in storage pools reserved for the application. Reserve slower devices for a volume dedicated to less demanding or supporting applications.

ÂTo increase parallelism, spread LUNs across different Xserve RAID controllers. For example, instead of creating a single 4-disk LUN on one side of an Xserve RAID, create two 2-disk LUNs, one on each side, and add these LUNs to a storage pool.

Xsan then stripes data across the two LUNs and benefits from simultaneous transfers through two controllers.

ÂTo increase parallelism in a relatively small storage pool (the size of one or a few drive modules), create a slice of similar size across all the drives on a controller instead of creating the storage pool from just one or two drive modules.

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ÂSpread file transfers across as many drives and RAID controllers as possible. Try creating slices across the drives in RAID systems, then combine these slices into a storage pool.

ÂTo increase throughput, connect both ports on client Fibre Channel cards to the fabric and set the multipathing method for the storage pool to Rotate.

ÂStore user files, file system metadata, and journal data on separate storage pools, and create these storage pools using LUNs from different RAID controllers.

ÂUse a router to isolate the Ethernet network used by the SAN from a company intranet or the Internet, or better, use a second Ethernet network (including a second Ethernet card in each SAN computer) for the SAN.

ÂIf your SAN uses directory services, mail services, or other services on a separate server, use a second, separate Ethernet network to connect SAN computers to that server.

ÂAs a rule of thumb, consider that a single Xserve RAID controller, after file system overhead, can transfer roughly 80 MB of user data per second (160 MB per Xserve RAID system). If your SAN must support an application running on multiple clients that requires specific throughput on each client, you can use this number to estimate the number of Xserve RAID systems necessary to support the aggregate transfer rate.

Availability Considerations

If high availability is important for your data, set up at least one standby controller in addition to your primary controller. Also, consider setting up dual Fibre Channel connections between each client, controller, and storage device using redundant Fibre Channel switches.

Important: Losing a metadata controller without a standby can result in the loss of all data on a volume. A standby controller is recommended.

Also, if you have a standby controller, you can upgrade the Xsan software without interrupting the SAN. For more information, see “Upgrading Controller Software” on page 87.

Security Considerations

If your SAN will support projects that need to be completely secure and isolated from each other, you can create separate volumes for each project to eliminate any possibility of the wrong client or user accessing files stored on a volume.

As SAN administrator, you control which client computers can use a volume. Clients can’t browse for or mount SAN volumes on their own. You use Xsan Admin to specify which clients a volume is mounted on.

You can also assign user and group permissions to folders you create on a volume or use standard file access permissions to control access to other items.

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Choosing RAID Schemes for LUNs

Much of the reliability and recoverability of data in a SAN is not provided by Xsan itself but by the RAID arrays you combine to create your storage pools and volumes. Before you set up a SAN, you use RAID Admin to prepare LUNs based on specific RAID schemes.

Important: If a LUN belonging to an Xsan volume fails and can’t be recovered, all data on the volume is lost. It is strongly recommended that you use only redundant LUNs (LUNs based on RAID schemes other than RAID 0) to create your Xsan volumes.

LUNs configured as RAID 0 arrays (striping only) or LUNs based on single drives are difficult or impossible to recover if they fail. Unprotected LUNs such as these should only be used for volumes that contain scratch files or other data that you can afford to lose.

Xserve RAID systems ship already configured as recoverable, redundant RAID 5 arrays.

Xserve RAID supports all popular RAID levels. Each RAID scheme offers a different balance of performance, data protection, and storage efficiency, as summarized in the following table.

RAID level

Storage efficiency

Read performance

Write performance

Data redundancy

RAID 0

Highest

Very High

Highest

No

 

 

 

 

 

RAID 1

Low

High

Medium

Yes

 

 

 

 

 

RAID 3

High to very high

Medium

Medium

Yes

 

 

 

 

 

RAID 5

High to very high

High

High

Yes

 

 

 

 

 

RAID 0+1

Low

High

High

Yes

 

 

 

 

 

RAID 10, 30, and 50 schemes assume the use of AppleRAID software striping and aren’t appropriate for use with Xsan, which performs its own striping. For more help choosing RAID schemes for your arrays, see the Xserve RAID User’s Guide or the Xserve RAID Technology Overview (at www.apple.com).

Deciding on the Number of Volumes

A volume is the largest unit of shared storage in the SAN. If your users need shared access to files, you should store those files on the same volume. This makes it unnecessary for them to pass copies of the files among themselves.

On the other hand, if security is critical, one way to control client access is to create separate volumes and mount only the authorized volume on each client.

For a more typical balance of security and shared access, a flexible compromise is to create a single volume and use folder access privileges to control access.

Note: The maximum size of a volume is 16 TB in Mac OS X v10.3 and 1024 TB in

Mac OS X v10.4. If you need more storage, you need to create more than one volume.

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Deciding How to Organize a Volume

You can help users organize data on a volume or restrict users to specific areas of the volume by creating predefined folders. You can control access to these folders by assigning access permissions using Xsan Admin.

You can assign folders to specific storage pools using affinities. You can, for example, create a folder for data that requires fast access and assign that folder to your fastest storage pool.

Assigning LUNs to Storage Pools

You should set up a storage pool using LUNs that have similar capacity and performance characteristics.

To provide high performance, Xsan uses the RAID 0 scheme to stripe data across the LUNs in a storage pool. This requires that the LUNs in the pool be the same size. If you set up a storage pool using LUNs of different sizes, Xsan uses available space on each LUN equal to the capacity of the smallest LUN. If the LUNs vary in size, this can result in wasted capacity. For example, if you assign 240 GB and 360 GB RAID arrays to a storage pool, 120 GB of the larger array will not be used. By combining LUNs with similar capacities, you avoid wasting available storage.

If you want to set up a storage pool for use by a high performance application, assign similarly high speed LUNs. Assign slower LUNs to a storage pool where you keep data that doesn’t have critical performance requirements.

Creating storage pools from LUNs that are hosted on different drive modules and different RAID controllers increases performance by increasing the parallelism of data transfers. For example, a storage pool consisting of two LUNs, each a single drive module on the left side of an Xserve RAID, will not be as fast as a similarly sized storage pool made up of two LUNs that are single slices across all seven drives, one slice on each controller. In the first case, all transfers go through a single RAID controller to just two drives; in the second case the same transfer is spread across two RAID controllers and fourteen drives.

Assigning Storage Pools to Volumes

After you decide how to combine available LUNs into storage pools, assign the storage pools to the volumes you want to create.

For best performance, create separate storage pools for file system metadata and journal data.

Note: No storage pool or volume can be larger than 16 TB (Mac OS X v10.3) or 1024 TB (Mac OS X v10.4).

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Deciding Which Clients to Mount a Volume On

If you create multiple volumes, decide which volumes should be mounted on which clients.

Choosing Controllers

You must choose at least one computer to be the SAN controller, the computer that is responsible for managing file system metadata.

Note: File system metadata and journal data are stored on selected SAN volumes, not on the controller itself. For more information, see “Choosing Where to Store Metadata and Journal Data” on page 30.

If you have a small number of clients or if performance is not critical you can use a single computer as both controller and client. You can even set up a SAN consisting of a single storage device and a single computer that acts as both controller and client (to provide network attached storage, for example).

If high availability is important, you should use at least two controllers, one as the primary controller and one as a standby. You can specify additional controllers as needed, and set their failover priorities to determine the order in which they are tried if the primary controller stops responding.

Choosing Standby Controllers

To be sure that SAN volumes are always available, set up at least one standby controller that can take over if your primary metadata controller fails. A standby controller also makes it possible for you to upgrade software on the controllers without interrupting user access to SAN volumes.

Combining Clients and Controllers

The same computer can function as both a metadata controller and a client. It’s possible, for example, to set up a SAN consisting of a single Xserve RAID and one computer that acts as both controller and client. Any computer you specify as a controller can also act as a client.

If, for example, you don’t have a computer to dedicate as a standby controller, you can assign a computer that is normally used as a client to take over controller duties if the primary controller fails.

To keep clients and controllers separate, you can set up client-only computers for your users.

Choosing Where to Store Metadata and Journal Data

The metadata and journal data that describe a volume are not stored on the volume’s metadata controller but on the volume itself. By default, they are stored on the first storage pool in the volume. If the volume consists of more than one storage pool, you can choose which storage pool is used to store metadata and journal data.

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