Seagate STT20000N, Product Manual

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Chapter 5 SCSI Interface
Page 42 STT20000A Product Manual
Command set changes to Incorporate RWW and HDC
The following changes have been implemented in both the SCSI and ATAPI
command sets to support of Read While Write and hardware data compression.
Included are methods for detecting the presence of each feature.
Read-While-Write
Log Sense Write Error Counts page code (02h)
Log Sense page code 02h (Write Error Counts) has been added to the Seagate tape
drives that have read while write (RWW) capabilities. A Seagate tape drive that
supports read while write can be detected by requesting the available Log Sense
pages (Log Sense page code 0), then noting support for Log Sense page 2 (Write
Error Counts). The Log Sense page code 2 parameter codes for write errors are
listed in the following table:
Parameter Code Length in Bytes Name
0002 4 Total Rewrites
8010 4 Rewrites even tracks
8011 4 Rewrites odd tracks
The total rewrite count is incremented each time a block is determined bad in the
RWW check and rewritten to tape. It also represents the sum of the Rewrites even
tracks and Rewrites odd tracks. The Rewrites even tracks is incremented if the bad
block is located on an even track. The Rewrites odd tracks is incremented if the bad
block is located on an even track.