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Product Manual - Disc Drive SCSI-2/SCSI-3 Interface (Vol. 2; Ver. 2), Rev. E 163
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[5] Write Retention Priority:
The cache replacement algorithm does distinguish between retention in the cache of host-requested
data and prefetch data. Therefore, this half byte is always 0.
[6] Disable Pre-fetch Transfer Length:
Prefetch is disabled for any SCSI Read command whose requested transfer length exceeds this value.
[7] Minimum Pre-fetch:
Specifies the minimum number sectors to pre-fetch, regardless of the delay it may cause to other com-
mands.
[8] Maximum Pre-fetch:
Specifies the maximum number of logical blocks that may be pre-fetched. The pre-fetch operation may
be aborted before the maximum pre-fetch value is reached, but only if the minimum pre-fetch value has
been satisfied.
[9] The maximum Pre-fetch Ceiling field specifies an upper limit on the number of logical blocks computed
as the maximum pre-fetch. If the Maximum Prefetch value is greater than the Maximum Pre-fetch ceiling
the value is Truncated to the Maximum Pre-fetch Ceiling value.
[10] FSW: The Force Sequential Write (FSW) bit (Bit 7 Byte 12). When set to one, indicates that multiple block
writes are to be transferred over the SCSI bus and written to the media in an ascending, sequential,
logical block order. When the FSW bit equals zero, the target is allowed to reorder the sequence of
writing addressed logical blocks in order to achieve a faster command completion.
[11] DRA: The Disable Read-Ahead (DRA) bit (Bit 5 Byte 12), when set to one, requests that the target not
read into the buffer any logical blocks beyond the addressed logical block(s). When the DRA bit equals
zero, the target may continue to read logical blocks into the buffer beyond the addressed logical block(s).
[12] Number of Cache Segments:
The Number of Cache Segments byte (Byte 13) gives the number of segments into which the host
requests the drive divide the cache.
[13] Cache Segment Size:
The Cache Segment Size field (Bytes 14 and 15) indicates the requested segment size in Bytes. This
standard assumes that the Cache Segment Size field is valid only when the SIZE bit is one.
[14] Non-Cache Segment Size:
If the Non-Cache Buffer size field (Bytes 17-19) is greater than zero, this field specifies to the target the
number of bytes the initiator requests that the target allocate for a buffer function when all other cache
segments are occupied by data to be retained. If the number is at least one, caching functions in the
other segments need not be impacted by cache misses to perform the SCSI buffer function. The impact
of the Non-Cache Buffer Size equal 0 or the same of this field plus the Cache Segment Size greater than
the buffer size is vendor specific.
[15] LBCSS:
Logical block cache segment size. Not used at this time.
In addition to the caching control provided by the Caching Mode page, some 10-byte commands contain
control bits DPO and FUA the intent of which is override the cache page control bits.