Product manual

SCSI Description
Maxtor Atlas 10K IV 5-47
Table 5-69 Caching Page - Field Descriptions
Field
Default
Value
Description
PS 1
Parameters Savable. This bit is only used with the MODE SENSE command. A
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.
WCE 1
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 thedata to the
media.
When WCE = 1, write-back caching is enabled whileprocessing aWRITE 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
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:
•AWREto1
•RCto0
•DCRto0
•CorrectionSpansetto170
• Head Offset to 0
•ServoOffsetto0
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.
RCD 0
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
READ command.
When the value is 1, read caching is disabled and the data returned in response
toa READ commandis fetched from themedium and not from thedrive’s cache
memory.
Demand Read Re-
tention
Priority
0
This field advises the drive on the retention priority to assign data read into the
cache that has also been transferred from the drive to theinitiator.Not supported
by the drive.
Demand Write Re-
tention
Priority
0
This field advises the drive on the retention priority to assign data written into
the cache that has also been transferred from the cache memory to the medium.
Not supported by the drive.
Disable
Pre-Fetch Transfer
Length
FFFFh
This field specifies the selective disabling of anticipatory pre-fetch
on long transfer lengths. The value in this field is compared to the number of
sectors requested by the current READ command. If the number of sectors is
greater the than the value specified, anticipatory pre-fetch is not performed for
the command. When 0, anticipatory pre-fetch is disabled. Ignored by the drive.
Minimum
Pre-fetch
0
This field indicates the number of sectors that are to be pre-fetched. See also
MF.
Maximum
Pre-fetch
0x7F5
This field indicates the maximum amount of data to pre-fetch into the cache as
a result of one READ command. Not supported by the drive.
Maximum
Pre-fetch
Ceiling
0x7F5
Specifies an upper limit on the number of logical blocks computed as the max-
imum pre-fetch. If this number of sectors is greater than the maximum pre-
fetch, then the number of logical blocks to pre-fetch is reduced to the value
stored in the maximum pre-fetch ceiling field. Not supported by the drive.
FSW 0 The Force Sequential Write bit. Not supported by the drive.
LBCSS 0 The Logical Block Cache Segment Size bit. Not supported by the drive.
DRA 0 The Disable Read-Ahead bit. Not supported by the drive.