NOTES:

 

 

Bytes 12 to 19 are returned only if the device operating definition is SCSI-3.

 

 

Table 5-67Caching Page - Field Descriptions

 

 

 

 

Field

 

Default

Description

 

Value

 

 

 

 

 

 

 

 

 

 

Parameters Savable. This bit is only used with the MODE SENSE command. A

PS

 

1

returned value of 1 indicates that the target is capable of saving the page in a

 

non-volatile, vendor-specific location. Bit reserved with MODE SELECT com-

 

 

 

 

 

 

mand.

 

 

 

 

 

 

 

An initiator control (ic) enable bit set to one specifies that the device server use

IC

 

0

the NUMBER OF CACHE

 

SEGMENTS field or the CACHE SEGEMENT SIZE field, dependent upon the

 

 

 

SIZE bit, to control the caching algorithm rather than the device server’s own

 

 

 

adaptive algorithm.

ABPF

 

0

Enable Abort Prefetch. When set, this bit requests the device abort pre-fetch

 

work on the receipt of a new command.Ignored by the drive

 

 

 

 

 

 

A caching analysis permitted (cap) bit set to one specifies that the device server

CAP

 

0

perform caching analysis during subsequent operations. A cap bit set to zero

 

specifies that the caching analysis be disabled to reduce overhead time or to pre-

 

 

 

 

 

 

vent non pertinent operations from impacting tuning values.

 

 

 

 

 

 

 

A discontinuity (DISC) bit set to one specifies that the device server continue

DISC

 

0

the pre-fetch across time discontinuities (e.g., across cylinders) up to the limits

 

of the buffer, or segment, space available for the pre-fetch. A DISC bit set to

 

 

 

zero specifies that pre-fetches be truncated or wrapped at time discontinuities.

 

 

 

ignored by drive.

Size

 

0

Specifies which of two fields are used to configure the cache. When Size=0, the

 

Number of Cache Segments field is used. When Size=1, the Cache Segment

 

 

 

Size field is used.

 

 

 

Write Cache Enable. The default value of 1 enables write-back caching when

 

 

 

processing a WRITE command. When set to 0 the drive returns a GOOD status

 

 

 

and COMMAND COMPLETE only after successfully writing all the data to the

 

 

 

media.

 

 

 

When WCE = 1, write-back caching is enabled while processing a WRITE com-

 

 

 

mand. The drive returns a GOOD status and COMMAND COMPLETE only af-

 

 

 

ter fetching the data from the initiator and placing it in the drive’s cache

WCE

 

1

memory.

 

Note: For maximum data integrity, it is strongly recommended that when WCE

 

 

 

 

 

 

is set to 1, the Read-Write Error Recovery Page (01h) fields be set as follows:

 

 

 

• AWRE to 1

 

 

 

• RC to 0

 

 

 

• DCR to 0

 

 

 

• Correction Span set to 170

 

 

 

• Head Offset to 0

 

 

 

• Servo Offset to 0

MF

 

0

Multiplication Factor (value must be 0). The drive interprets the minimum and

 

maximum pre-fetch fields values in terms of the number of logical blocks for

 

 

 

each of the respective types of prefetch.

 

 

 

Read Cache Disable. The default value of 0 enables the read cache capability

 

 

 

and allows the drive to use cache-resident data or medium data to satisfy a

RCD

 

0

READ command.

 

When the value is 1, read caching is disabled and the data returned in response

 

 

 

 

 

 

to a READ command is fetched from the medium and not from the drive’s cache

 

 

 

memory.

Maxtor Atlas 10K V

5-45