1996 Seagate Technology, Inc. All rights reserved
Publication Number: 77767479 Rev. E
March 1996
Seagate, Seagate Technology and the Seagate logo are registered trademarks of Seagate Technology ,
Inc. Ha wk™, SeaF AX, SeaF one, SeaTDD and SeaBO ARD are trademarks of Seagate Technology,
Inc. Other product names are registered tr ademarks or trademarks of their owners.
Seagate reserves the right to change, without notice, product offerings or specifications. No par t of this
publication may be reproduced in any f orm without written permission of Seagate Technology , Inc.
Product Manual - Hawk 4 Famil y (Wide) SCSI-2 (Volume 1), Rev. E v
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Revision status summary sheet
RevisionAuthorityDateWriter/Eng.Sheets Affected
A Issue 03/13/95D . Ashbyv thru viii, 1 thru 70.
BPLD: 87201 06/26//95D . Ashby1/1, v and 18.
CPLD: 87236 08/30/95D. Ashby1/1, v and 39.
D PLD: 87305 1/24/96D . Ashby1/1, v , vi, 2, 12, 21 and 41
E PLD: 87334v and 18
Notice.
Product Manual 77767479 is Volume 1 of a tw o Volume document with the SCSI interface information
in the V olume 2 SCSI Interface Pr oduct Man ual, P/N 77738479.
If the SCSI Interface information is needed the Volume 2 Interface Manual should be ordered, P/N
77738479.
vi Product Manual - Hawk 4 Family (Wide) SCSI-2 (Volume 1), Rev. E
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viii Product Manual - Hawk 4 Family (Wide) SCSI-2 (Volume 1), Rev. E
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14.0Seagate Technical support services......................................................................................... 68
Product Manual - Hawk 4 Famil y (Wide) SCSI-2 (Volume 1), Rev. E 1
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1.0Scope
This Manual describes the Seagate Technology, Inc. Hawk 4 Family Disc Drive. This high capacity, high
performance member of the Seagate 3.5 inch rigid disc family is a companion product to the ST12400 drive
family . It has an embedded SCSI controller . Perf ormance information is given in Section 5. The Hawk 4 F amily
interface is defined for functional compatibility to a subset of the Seagate SCSI Interf ace Specification 77738479,
and the ANSI SCSI-2 and SCSI-3 standards. The Model Hawk 4 Family drives are classified as "Intelligent"
peripherals. The Ha wk 4 Family provides Le vel 2 conf ormance (highest level) with the ANSI SCSI-1 standard.
Details of the Hawk 4 F amily driv e SCSI implementation are provided in Section 11 of this manual, (Vol. 1)
and in the SCSI Interface Product Manual P/N 77738479 (Vol. 2; Ver. 2).
The Hawk 4 family of drives consists of the ST15230W/WD/WC/DC driv es.
From this point on in this Product Manual the ref erence to Ha wk 4 F amily is referred to as "the driv e" (unless
reference to individual models are necessary).
The drive printed circuit board is referred to as a PCB.
SEAGATE
* 68 pin SCSI I/O and 4 pin direct current power connector shown as used on "W" and "WD" models. "WC" and "DC"
drive models have a single 80 pin connector that contains both SCSI I/O and direct current power (see Figure 3.0-1).
Figure 1-1. Hawk 4 family (Wide) drive
2 Product Manual - Hawk 4 Family (Wide) SCSI-2 (Volume 1), Rev. D
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2.0Applicable standards and reference documentation
The drive has been developed as a system peripheral to the highest standards of design and construction.
The drive depends upon its host equipment to provide adequate power and environment in order to achie ve
optimum performance and compliance with applicable industry and governmental regulations. Special attention must be given in the areas of saf ety , power distrib ution, shielding, audible noise control, and temperature
regulation. In particular , the drive must be securely mounted in order to guarantee the specified perf ormance
characteristics. Mounting b y bottom holes m ust meet the requirements of Section 7.6.3.
2.1Standards
The Hawk 4 Family (Wide) complies with Seagate standards as noted in the appropriate sections of this
manual and the Seagate SCSI Interface Specification, P/N 77738479 (Vol. 2, Version 2).
The Hawk 4 F amily is a UL Recogniz ed component per UL 1950 and a CSA Certified component per CAN/
CSA-C22.2 No. 950-M89. It also meets the requirements of DIN VDE 0805:1993 and EN60950: 1992 (IEC
950).
The drive, as delivered, is designed for system integration and installation into a suitable enclosure prior to
use. As such the dr ive is supplied as a subassembly and is not subject to Subpart J of Part 15 of the FCC
Rules and Regulations nor the Radio Interference Regulations of the Canadian Department of Communications. Howev er, the unit has been tested using proper shielding and g rounding and found to be compliant with
Class A limits of the FCC Rules and the Regulations of The Canadian Department of Communications.
The physical design characteristics of the drive serve to minimize radiation when installed in an enclosure
that provides reasonable shielding. As such, the drive is capable of meeting the Class B limits of the FCC
Rules and Regulations of the Canadian Department of Communication. Howe ver , it is the users responsibility
to assure that the drive meets the appropriate EMI requirements in their system. Shielded I/O cab les may be
required if the enclosure does not provide adequate shielding. If the I/O cables are e xternal to the enclosure,
shielded cables should be used, with the shields grounded to the enclosure and to the host controller .
Caution.To avoid potential service problems, observe the follo wing precautions:
The Manufacturers installed labels must not be remo ved from the drive or cov ered with additional
labels, as they contain information required when servicing the product.
2.2Electromagnetic Compliance for the European Union
If this model has the CE Marking it complies with the European Union requirements of the Electromagnetic
Compatibility Directive 89/336/EEC of 03 May 1989 as amended by Directive 92/31/EEC of 28 April 1992 and
Directive 93/68/EEC of 22 July 1993.
Seagate uses an independent laboratory to confirm compliance to the above directives. The drive was tested
in a representative system for typical applications. The selected system represents the most popular
characteristics for test platforms. The system configurations include:
•486, Pentium, and Power PC Microprocessors•Keyboard
•3.5-inch Floppy Disc Drive•Monitor/Display
Although the test system with this Seagate model complies to the directives, we cannot guarantee that all
systems will comply. The computer manufacturer or system integrator shall confirm EMC compliance and
provide CE Marking for their product.
2.3Applicable reference documents
Installation Guide: Seagate P/N 77767477Product Manual: SCSI Interf ace Seagate P/N 77738479
ANSI Small Computer System Interface (SCSI): Document Number ANSI3.131-1986 (X3T9/84.40 Re v. 1B)
(X3T9.2/82-2 Rev. 17B), X3T9.2/86-109 Re vision 10H (SCSI-2) and X3T9.2-184 Re v. 4 (SCSI-3).
Seagate Package T est Requirements P/N 30190-001 (pac kages under 100 lbs)
Seagate Package Test Requirements P/N 30191-001 (pac kages o ver 100 lbs)
In case of conflict between this document and any referenced document, this document shall take precedence.
Product Manual - Hawk 4 Famil y (Wide) SCSI-2 (Volume 1), Rev. E 3
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3.0General description
The drives are a member of a family of low cost, high performance, highly reliable, random access storage
devices designed to meet the needs of the OEM marketplace.
The drive records and recovers data on 3.7 inch (95 mm) fix ed discs .
The drive supports the Small Computer System Interface-2 (SCSI) as described in the ANSI SCSI-1, SCSI-
2 and SCSI-3 Interface Specifications to the extent described in this product manual (Vol. 1), which defines
the product performance characteristics of the Hawk 4 Family of drives, and the SCSI Interface Product
Manual P/N 77738479 (Vol. 2, Version 2) which describes the general interface characteristics of this and
other families of Seagate 3.5-inch drives.
The drive interface supports multiple initiators, disconnect/reconnect, self configuring host software and automatic features that reliev e the host from the necessity of knowing the physical characteristics of the targets
(logical block addressing is used).
The Head/Disc Assembly (HDA) is environmentally sealed at the factory. Air recirculates within the HDA
through a nonreplaceable filter to maintain a contamination free head/disc environment.
Refer to Figure 3.0-1 for an e xploded view of the drive . NEVER disassemble the Head/Disc Assembly (HD A).
This exploded view is f or information only . Do not attempt to service items in the sealed environmental enclosure (heads, media, actuator , etc.) as this requires special facilities . The driv e contains no parts replaceable
by the user . The drive w arranty is voided if the HDA is opened.
The Hawk 4 Family (Wide) drives use a dedicated landing zone at the innermost radius of the media to
eliminate the possibility of destroying or degrading data b y landing in the data zone . The drive automatically
goes to the landing zone when the power is removed.
The Hawk 4 F amily (Wide) drives incorporate an automatic shipping lock which prevents potential damage to
the heads and discs that result from movement during shipping and handling. The shipping lock disengages
when power is applied to the drive and the head load process begins.
The Hawk 4 Family (Wide) dr ives decode Track 0 location from the dedicated ser vo surface to eliminate
mechanical transducer adjustments and related reliability concerns.
The Hawk 4 Family (Wide) drives use a high performance actuator assembly that consists of a low inertia,
balanced, patented, straight arm design that provides excellent performance with minimum power dissipation.
4 Product Manual - Hawk 4 Family (Wide) SCSI-2 (Volume 1), Rev. E
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“W/WD” Family PCB
Figure 3.0-1. Hawk 4 family (wide) drive
“WC/DC” Family PCB
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4.0Standard features
The Hawk 4 F amily (Wide) has the f ollowing standard f eatures:
• Integrated SCSI Controller
• Single Ended and Differential SCSI drivers and receivers
• Asynchronous and Synchronous data transfer protocol
• Firmware downloadable via SCSI interface
• Selectable sector size from 256 to 4096 bytes/sector
• Programmable sector reallocation scheme
• Flawed sector reallocation at format time
• Programmable auto write and read reallocation
• Reallocation of defects on command (P ost F ormat)
• 96 bit Reed-Solomon error correcting code
• Sealed Head/Disc Assembly
• No preventativ e maintenance or adjustment required
• Dedicated head landing zone
• Automatic shipping lock
• Automatic Adaptive Thermal Compensation
• Patented Tri-Phase Servo with embedded Grey Code track address to guarantee servo positioning.
• Self diagnostics performed at power on
• 1:1 Interleave
• Zoned Bit Recording (ZBR)
• V ertical, horizontal, or top down mounting
• Dynamic spindle brake
• 512 K byte data buff er
• Permanently mounted terminators (for model ST15230W only), enabled by installation of a jumper plug.
4.1Perf ormance
• Programmable multi-segmentable cache b uffer
• 5411 r/min Spindle. Average latency = 5.54 ms
• Command Queuing of up to 64 commands per initiator
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4.2Unformatted and f ormatted capacities
Formatted capacity depends on the number of spare reallocation sectors reserved and the number of bytes
per sector. The follo wing tab le shows some
Spare sectors or cylinders W/WD/WC/DC
reserved for reallocationMB
No spares43194596
Twelve spare sector per cylinder [2]
2 spare cylinders per Unit [3]42944546
One spare sector per cylinder
2 spare cylinders per Unit [3]43154590
Unformatted capacity 5170
Notes.
[1] Bytes per sector. Sector size selectable at format time. Users having the necessar y equipment may
modify the data block size before issuing a format command and obtain different formatted capacities
than those listed. User available capacity depends on spare reallocation scheme selected. See Mode
Select Command and Format Command in the SCSI Interface Product Manual P/N 77738479.
[2] All twelve spare sectors are on one track.
[3] Spare cylinders are on the two inner tracks.
typical
formatted capacities.
512 [1]1024 [1]
The standard OEM model is as follows:
Formatted Data Block Size*Unformatted
512 Byte/Sector
ST15230W/WD/WC/DC4294 MB5170 MB
*Twelve spare sectors per cylinder (all twelve spare sectors are on one track), two spare cylinders/unit.
Drives are shipped with Installation Guide 77767477 (unless otherwise requested), and a small bag of two
types of jumpers for the Option Select jumper headers.
4.3Options (factory installed)
The capacities shown in Section 4.2 are available upon request. Other capacities can be ordered depending
on sparing scheme and sector size requested.
The following options are incorporated at the time of production. See Section 12.0.
• Front panel (green LED)
• Single Unit shipping pack
4.4Optional accessories (user installed)
The following accessories are av ailab le . All kits may be installed in the field. See Section 13.0.
• Front P anel Kit (with green LED)
• Single Unit shipping pack kit
• Adapter Accessory Frame Kit P/N 75790701 (adapts 3.5-inch drives "W" and "WD" to fit in 5.25-inch drive
mounting space. Does not work for "WC" and "DC" driv es which plug directly into a b ulkhead connector.)
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4.5Installation
For option jumper locations and definitions refer to Figure 10.1-1. Drive default mode parameters are not
normally needed for installation. Refer to Section 11.3.2 for default mode parameters if they are needed.
• Ensure that the SCSI ID of the drive is not the same as the host adapter. Most host adapters use SCSI ID
7, which is the highest priority on both 8 and 16 bit data busses.
• If multiple devices are on the b us set the drive SCSI ID to one that is not presently used by other devices on
the bus.
• If the drive is the only device on the bus , attach it to the end of the SCSI bus cable. Permanently installed
terminators must be enabled on the drive for ST15230W models using a jumper plug (see Figure 10.1-1),
For ST15230WD/WC/DC models, terminators must be installed external to the drive . These e xternal terminators must be provided by the user , systems integrator or host equipment man uf acturer . Refer to section
11.6.4.3.
• If the drive is attached to a bus that contains other devices , and the new drive is not attached to the end of
the bus, the terminator enable jumper should be removed from the ne w drive .
• Set all appropriate option jumpers for desired operation prior to power on. If jumpers are changed after
power has been applied, recycle the drive power to mak e the ne w settings effective.
• Installation instructions are provided by host system documentation or with any additionally purchased
drive installation software. If necessary see section 14.0 for Seagate support services telephone numbers.
• The manufacturers installed labels must not be remo ved from the drive or cov ered with additional labels, as
they contain information required when servicing the product.
Formatting
• It is not necessary to low level format this drive. The drive is shipped from the factory low level f ormatted in
512 byte sectors.
• Reformat the drive if one of the following occurs .
- A different sector size is selected.
- A different spare sector allocation scheme is selected.
• High level for mat the drive. This involves assigning one or more par titions or logical drives to the drive
volume. F ollow the instructions in the system manuals for the system into which the driv e is to be installed.
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5.0Performance characteristics
5.1Internal drive characteristics (transparent to user)
Drive Capacity5170MByte (UNF)
Read/Write Heads19
Bytes/Track68155Bytes (UNF, Avg)
Bytes/Surface272Mbytes (UNF)
Tracks/Surface , T otal3992Tracks (user accessible)
Tracks/Inch4200TPI
Servo Heads11
Internal Data Rate33.9 to 61.0Mbits/sec (variable with z one)
Disc Rotational Speed5411 +0.5%r/min
Aver age Rotational Latency5.54ms
5.2SCSI Seek, Read and Write performance c haracteristics (visible to user) [8]*
Refer to Section 11.7 and to the SCSI-2 Interface Product Man ual 77738479 for additional timing details .
5.2.1Access time
Includes Controller Overhead
(without disconnect) [1] [4]
ReadWrite
ms
Average-Typical [3]10.411.4
Max.[2]11.913.4
Single T rack-Typical [3] 2.1 2.5
Max.[2] 3.8 4.3
Full Stroke-Typical [3]20.621.4
Max.[2]23.924.9
*[ ] All notes are listed in section 5.3.1
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5.2.2Format drive command execution time (minutes) [1]
Maximum (with verify)70 Min.
Maximum (no verify)45 Min
5.2.3Read data command execution time [4]
(512 byte sector size, without disconnect and with read look ahead cache disabled.)
Latency time is included.
a. From CDB reception to the drive request f or the first data byte to be transferred to the Host
1. Typical (Zero Stroke Seek) 7.32 ms [3]*
2. Typical (Av er age Seek)16.84 ms [3]
3. Maximum (Full Stroke Seek)31.38 ms [2]
b. Single Sector Read and Transfer of data to Host (time from receipt of last byte of the CDB to the request
for a status byte transfer to Host) [7].
1. Typical (Zero Stroke Seek) 7.42 ms [3]
2. Typical (Av er age Seek)16.95 ms [3]
3. Maximum (Full Stroke Seek)31.49 ms [2]
5.2.4Write data command execution time [4]
(512 byte sector size, without disconnect and with read look ahead disabled.) Latency
time is included.
a. From CDB reception to the request f or the first b yte of write data from the Host.
1. Typical 1.49 ms2. Maximum1.61 ms
b. Single Sector Write and Data Transfer from Host [7] [6]
(Time from receipt of the last byte of the CDB to the request for a completion status transf er to the Host)
1. Typical (Zero Stroke Seek) 7.72 ms [3]
2. Typical (Av er age Seek)17.10 ms [3]
3. Maximum (Full Stroke Seek)31.93 ms [2]
*[ ] All notes are listed in Section 5.3.1.
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5.3Generalized performance characteristics
Minimum Sector Interleave 1 to 1
Data Buffer To/From Disc Media
Data transfer rate (< 1 sector) - 512 Byte Sector
Min. [4]*4.33 MByte/sec
Avg. [4]6.15 MByte/sec
Max. [4]7.63 MByte/sec
Data Buffer To/From Disc Media
Data Transfer Rate (< 1 T r ac k) - 512 Byte Sector
Min. [4] 3.64 MByte/sec divided by (Interleave Factor)
Avg. [4] 5.16 MByte/sec divided by (Interleave F actor)
Max. [4] 6.41 Mbyte/sec divided by (Interleave Factor)
SCSI Interface Data
Transfer Rate (Asynchronous) [5]
-Maximum A v erage3.1 MBytes/sec [11]2.4 MBytes/sec
Sector Sizes512 user data blocks (default)
Variable (256 to 4096 bytes per sector) in even number of bytes per sector. If n (number of bytes
per sector) is odd, then n-1 will be used.
Synchronous T ransfer Rate
From 1.25 MByte/sec to 10.0 MBytes/sec (See section 11.5.)
Read/Write consecutive sectors on a trackYes
Flaw reallocation performance impact (For fla ws reallocated using the spareNegligible
sectors per track reallocation scheme.) [10]
Flaw reallocation performance impact (For fla ws reallocated using the spareNegligible
sectors per cylinder reallocation scheme.) [10]
Flaw reallocation performance impact (For flaws reallocated using the spare trac ks35 ms (typical)
per volume reallocation scheme.)
Overhead time for head switch (512 byte sectors)1 ms
Overhead time for one trac k cylinder switch<3 ms Typical
Aver age rotational latency5.54 ms
*[ ] All notes are listed in Section 5.3.1.
[1] Execution time measured from receipt of the last Byte of the Command Descriptor Block (CDB) to the
request for a Status Byte Transfer to the Initiator (excluding connect/disconnect).
[2] Maximum times are specified over the worst case conditions of temperature, v oltage margins and drive
orientation. When comparing specified access times, care should be taken to distinguish between typical
access times and maximum access times. The best comparison is obtained by system benchmark tests
conducted under identical conditions. Maximum times do not include error reco v ery.
[3] Typical access times are measured under nominal conditions of temperature, voltage, and horizontal
orientation as measured on a representative sample of drives.
[4] Assumes no errors and no sector has been relocated.
[5] Rate measured from the start of the first sector transfer to or from the Host.
[6] Assumes the Initiator immediately sends Write Data to the drive when requested.
[7] Command execution requires a data transf er phase (data to or from the disc media). Assumes the initia-
tor is instantly ready to send/receive the data when the drive generates first request for a data byte
transfer, and assumes an average data transfer rate between the drive and the Initiator as specified in
section 5.3.
[8] All performance characteristics assume that automatic adaptive temperature compensation is not in
process when the SCSI command is received. The following par ag raphs give highlights of thermal cali-
bration operation.
a. At spin-up, all heads are calibrated on the outer and inner diameter calibration tr ac ks.
b. A timed calibration occurs 1 minute after spin-up, and every 10 minutes thereafter. During these
timed calibrations, the firmware alternates between the inner and outer diameter calibration tracks.
For example, all heads are calibrated on the inner track, then 10 minutes later all heads are calibrated on the outer track. Automatic adaptive temperature calibration does not interrupt SCSI commands being executed.
c. If automatic adaptive thermal calibration is in process when the drive receiv es a SCSI command, the
drive queues the command until the compensation for the specific head being compensated completes. When compensation completes f or the specific head being compensated, the drive e xecutes
the first queued command. When execution of the first queued command completes, the drive continues compensation for the remaining head(s). The abov e procedure contin ues until the drive completes compensation for all heads.
d. When a timed calibration comes due, the drive postpones the calibration until the drive has been idle
for 25 to 50 milliseconds.
e. When the drive receives a Write command, the drive perf orms a single head calibration if a calibra-
tion has been delayed f or 1 to 5 minutes. The driv e performs an uninterruptible calibration of all heads
if the calibration has been delayed more than 5 minutes .
f.The drive preforms a calibration of all heads prior to the first retr y of any media error if a timed
calibration has been delayed f or o v er one minute .
g. Automatic adaptive temperature compensation tak es less than 0.1% of b us time.
h. Automatic adaptive temperature compensation occurs at times other than mentioned above, but
should be transparent to the user (e.g., during execution of Format, Rezero, and Reassign Block
commands).
i.A rezero command can be used to reset the Automatic adaptive temperature compensation timer
back to start so that the host can know when the interruption for timed thermal compensation will
occur.
[9] Assumes system ability to support 5.2 Mb/s and no cable loss.
[10]Simulated
[11]Assumes Typical host delays and cable losses.
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5.4Start/stop time
After DC power has been applied, the drive becomes ready within 25 seconds if the Motor Start Option is
disabled (i.e. the motor starts as soon as the power has been applied). During this time the drive responds to
some commands over the SCSI interface* in less than 3 seconds . Stop time is 20 seconds from removal of
DC power .
If the Motor Start Option is enabled the internal controller accepts the commands listed in the SCSI Interface
Product Manual* less than 3 seconds after DC power has been applied. After the Motor Start Command has
been received the drive becomes ready for normal operations within 25 seconds . The Motor Start Command
can also be used to command the drive to stop the spindle*.
There is no power control switch on the drive .
5.5Prefetch/multi-segmented cac he control
The drive provides prefetch (read look-ahead) and multi-segmented cache control algorithms that in many
cases can enhance system performance. “Cache” as used herein refers to the drive buffer storage space
when it is used in “cache” oper ations. To select prefetch and cache features the host sends the Mode Select
command with the proper values in the applicable bytes in Mode Page 08h*. Prefetch and cache operation
are independent features from the standpoint that each is enabled and disab led independently via the Mode
Select command. Ho wev er, in actual operation the pref etch feature overlaps cache oper ation somewhat as is
noted in sections 5.5.1 and 5.5.2.
All default cache and prefetch Mode par ameter values (Mode Page 08h) for standard OEM versions of this
drive family are given in Tables 11.3.2-1 and 11.3.2-2.
5.5.1Cache operation
In general, 448 Kbytes of the 512 Kbytes of ph ysical buff er space in the driv e can be used as storage space
for cache operations. The buffer can be divided into logical segments (Mode Select P age 08h, byte 13) from
which data is read and to which data is written. The drive maintains a table of logical block disk medium
addresses of the data stored in each segment of the buffer. If cache operation is enabled (RCD bit = 0 in
Mode Page 08h, byte 2, bit 0. See SCSI Interface Product Manual*), data requested by the host with a Read
command is retrieved from the buffer (if it is there), before any disc access is initiated. If cache operation is
not enabled, the buff er (still segmented with required number of segments) is still used, but only as circular
buffer segments during disc medium read operations (disregarding Prefetch operation f or the moment). That
is, the drive does not check in the buffer segments for the requested read data, but goes directly to the
medium to retrieve it. The retriev ed data merely passes through some buff er segment on the way to the host.
For a cache miss, all data transf ers to the host are in accordance with “buffer-full” r atio rules. On a cache hit
the drive ignores the buffer full ratio . See explanations associated with Mode page 02h (disconnect/reconnect
control) in the SCSI Interface Product Manual*.
The following is a simplified description of a read operation with cache operation enab led:
Case A - A Read command is received and the first logical block (LB) is already in cache:
1.Drive transfers to the initiator the first LB requested plus all subsequent contiguous LB’s that are already in the cache. This data may be in multiple segments.
2.When the requested LB is reached that is not in any cache segment, the drive fetches it and any
remaining requested LB’s from the disc and puts them in a segment of the cache. The driv e transfers
the remaining requested LB’s from the cache to the host in accordance with the disconnect/reconnect
specification mentioned above.
3.If the prefetch feature is enab led, ref er to section 5.5.2 f or oper ation from this point.
Case B - A Read command requests data, the first LB of which is not in any segment of the cache:
1. The drive fetches the requested LB’ s from the disc and transf ers them into a segment, and from there to
the host in accordance with the disconnect/reconnect specification referred to in case A.
2. If the prefetch feature is enab led, ref er to section 5.5.2 f or operation from this point.
Each buffer segment is actually a self-contained circular stor age (wraparound occurs), the length of which is
an integer number of disc medium sectors. The wraparounds capability of the individual segments greatly
enhances the buffer’s overall performance as a cache storage, allowing a wide range of user selectable
configurations, which includes their use in the prefetch operation (if enab led), e ven when cache operation is
disabled (see section 5.5.2). The
the
size
can not be directly selected.
specification. The siz e in Kbytes of each segment is reported by the Mode Sense command page 08h, bytes
14 and 15. If a size specification is sent by the host in a Mode Select command (bytes 14 and 15) no new
segment size is set up by the drive, and if the "STRICT" bit in Mode page 00h (b yte 2, bit 1) is set to one, the
drive responds as it does for any attempt to change unchangeab le parameters (see SCSI I/O Product Manual*).
The ST15230 family of drives supports operation of any integer number of segments from 1 to 16.
5.5.2Prefetch operation
If the Prefetch feature is enab led, data in contiguous logical blocks on the disc immediately be yond that which
was requested by a Read command can be retriev ed and stored in the buff er for immediate transf er from the
buffer to the host on subsequent Read commands that request those logical blocks (this is true even if
"cache" operation is disabled). Though the prefetch operation uses the buffer as a "cache", finding the requested data in the buffer is a prefetch “hit”, not a "cache" operation "hit". Prefetch is enabled using Mode
Select page 08h, byte 12, bit 5 (Disable Read Ahead - DRA bit). DRA bit = 0 enables prefetch. Since data that
is prefetched replaces data already in some buff er segment(s), the host can limit the amount of prefetch data
to optimize system performance.
number
Size
of segments may be selected using the Mode Select command, but
is selected only as a by-product of selecting the segment
number
The max prefetch field (bytes 8 and 9) limits the amount of prefetch. The drive does not use the prefetch
"ceiling field" (bytes 10 and 11).
During a prefetch operation, the drive crosses a cylinder boundary to fetch more data
(DISC) bit is set to one in bit 4 of byte 2 of Mode parameters page 08h.
Whenever pref etch (read look-ahead) is enabled (enab led by DRA = 0), it operates under the control of ARLA
(Adaptive Read Look-Ahead). If the host uses software interleave, ARLA enables prefetch of contiguous
blocks from the disk when it senses that a prefetch "hit" will lik ely occur, even if two consecutive read operations were not for physically contiguous blocks of data (e.g. "software inter leave"). ARLA disables prefetch
when it decides that a prefetch "hit" will not likely occur . If the host is not using software interleave, and if two
sequential read operations are not for contiguous blocks of data, ARLA disables prefetch, but as long as
sequential read operations request contiguous blocks of data, ARLA k eeps prefetch enab led.
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5.6Caching write data
Write caching is a write operation by the drive that makes use of a drive buff er storage area where the data to
be written to the medium is stored in one or more segments while the drive performs the write command.
Write caching is enabled along with read caching. For write caching, the same buffer space and segmentation is used as set up for read functions. The buffer segmentation scheme is set up or changed independently,
having nothing to do with whether or not read and write caching is enabled or disabled. When a write command is issued, the cache is first checked to see if any logical b locks that are to be written are already stored
in the cache from a previous read or write command. If there are, the respective cache segments are cleared.
The new data is cached for subsequent Read commands.
If the number of write data logical blocks exceeds the siz e of the segment being written into when the end of
the segment is reached, the data is written into the beginning of the same cache segment, overwriting the
data that was written there at the beginning of the operation. Howe ver , the drive does not o verwrite data that
has not yet been written to the medium.
Tables 11.3.2-1 and 11.3.2-2 show Mode default settings f or the Ha wk 4 f amily of driv es.
Product Manual - Hawk 4 Family (Wide) SCSI-2 (Volume 1), Rev. E 15
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6.0Reliability specifications
The following reliability specifications assume correct host/drive operational interf ace, including all interf ace
timings, power supply voltages , environmental requirements and drive mounting constr aints (see 7.6.3).
Seek ErrorsLess than 1 in 107 seeks
Read Error Rates [1]
Unrecovered DataLess than 1 sector in 10
Miscorrected DataLess than 1 sector in 10
MTBF800,000 hours
Service Life5 years
Preventiv e MaintenanceNone required
Note.[1]Error rate specified with automatic retr ies and data correction with ECC enabled and all flaws
reallocated.
6.1Error rates
The error rates stated in this specification assume the following:
a. The drive is operated per this specification using DC Po wer as defined in this specification (see Section
7.2).
b. The drive has been formatted with the SCSI FORMAT commands.
c. Errors caused by media defects or host system failures are excluded from error rate computations . Refer
to Section 8.0, Media Characteristics.
14
bits transferred
21
bits transferred
6.1.1Read errors
Before determination or measurement of read error rates:
a. The data that is to be used for measurement of read error rates must be v erified as being written correctly
on the media.
b. All media defect induced errors must be e xcluded from error rate calculations .
6.1.2Environmental interference
When evaluating systems operation under conditions of Electromagnetic Interf erence (EMI), the performance
of the drive within the system shall be considered acceptable if the drive does not generate an unrecov erable
condition.
An unrecoverable error, or condition, is defined as one that:
1. Is not detected and corrected by the drive itself;
2. Is not capable of being detected from the error or fault status provided through the drive or SCSI inter-
face; or
3. Is not capable of being recovered b y normal drive or system recov ery
procedures without operator intervention.
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6.1.3Write errors
Write errors can occur as a result of media defects, environmental interference, or equipment malfunction.
Therefore, write errors are not predictable as a function of the number of bits passed.
If an unrecoverable write error occurs because of an equipment malfunction in the driv e, the error is classified
as a failure affecting MTBF. Unrecoverable write errors are those which cannot be corrected within two
attempts at writing the record with a read verify after each attempt (excluding media defects).
6.1.4Seek errors
A seek error is defined as a failure of the drive to position the heads to the addressed trac k. There shall be no
more than one recoverable seek error in 107 physical seek operations. After detecting an initial seek error,
the drive automatically reseeks to the addressed track up to 3 times. If a reseek is successful, the Extended
Sense reports a seek positioning error (15h), no seek complete error (02h), or track follow error (09h), and
the sense key reports a recovered error (1h). If all three reseeks fail, a seek positioning error (15h) is reported
with a Medium (3h) or Hardware error (4h) reported in the Sense Key. This is an unrecoverable seek error.
Unrecoverable seek errors are classified as failures for MTBF calculations. Ref. section 5.1.1.2 of SCSI-2
Interface Product Manual P/N 77738479 f or Request Sense command information.
6.2Reliability and service
6.2.1Mean time between failure
The production disc drive shall achieve an MTBF of 800,000 hours when operated in a benign atmosphere at
an average disc drive ambient temperature of 95°F (35°C) or less as measured per this Product Manual,
Section 7.4.1. Short term excursions up to the specification limits of the operating environment will not aff ect
MTBF performance.
The following expression defines MTBF:
MTBF per measurement period =
Estimated power-on operation hours means power-up hours per disc drive times the total number of disc
drives in service. Each disc drive shall have accumulated at least nine months of operation. Data shall be
calculated on a rolling average base f or a minimum period of six months.
Drive failure means any stoppage or substandard performance caused by drive malfunction.
6.2.2Preventive maintenance
No routine scheduled preventiv e maintenance shall be required.
6.2.3Service life
The drive shall have a useful service life of fiv e years. Depot repair or replacement of major parts is permitted
during the lifetime (6.2.4).
Estimated power-on operating hours in the period
Number of drive failures in the period
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