Seagate ST373454 Manual download pdf (Page 19)

Cheetah 15K.3 SCSI Product Manual, Rev. G 9

Sector Sizes:

Default 512 byte user data blocks

Variable 512 to 528 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.

Notes for Section 4.2.

[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] Typical access times are measured under nominal conditions of temperature, voltage, and horizontal ori-

entation as measured on a representative sample of drives.

[3] Assumes no errors and no sector has been relocated.

[4] Assumes system ability to support the rates listed and no cable loss.

[5] Access time = controller overhead + average seek time and applies to all data transfer commands.

Access to data = access time + latency time.

4.3 Start/stop time

After DC power at nominal voltage has been applied, the drive becomes ready within 20 seconds if the Motor

Start Option is disabled (i.e., the motor starts as soon as the power has been applied). If a recoverable error

condition is detected during the start sequence, the drive executes a recovery procedure which may cause the

time to become ready to exceed 20 seconds. During spin up to ready time the drive responds to some com-

mands over the SCSI interface in less than 3 seconds after application of power. Stop time is 30 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 20 seconds typically (excluding an error

recovery procedure). The Motor Start Command can also be used to command the drive to stop the spindle

(see the

SCSI Interface Product Manual

There is no power control switch on the drive.

4.4 Prefetch/multi-segmented cache 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 operations. 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 (see the

SCSI Interface Product Manual

Prefetch and cache operation are independent features from the standpoint that each is enabled and disabled

independently via the Mode Select command. However, in actual operation the prefetch feature overlaps

cache operation somewhat as is noted in Section 4.5.1 and 4.5.2.

All default cache and prefetch Mode parameter values (Mode Page 08h) for standard OEM versions of this

drive family are given in Table 8.

4.5 Cache operation

In general, 7,077 kbytes of the physical buffer space in the drive can be used as storage space for cache oper-

ations. The buffer can be divided into logical segments (Mode Select Page 08h, byte 13) from which data is

read and to which data is written. The drive supports a maximum of 64 cache segments. The drive maintains a

table of logical block disc medium addresses of the data stored in each segment of the buffer. If cache opera-

tion is enabled (RCD bit = 0 in Mode Page 08h, byte 2, bit 0. See

SCSI Interface Product Manual

), data

Read/write consecutive sectors on a track Yes

Flaw reallocation performance impact (for flaws reallocated at format time using

the spare sectors per sparing zone reallocation scheme)

Negligible

Average rotational latency 2.00 msec

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