Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
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21.11 Write Cache
If the WCE (Write cache enable) bit is 1, the drive returns Good Status and Task complete message and goes to Bus Free
immediately after receiving the data of the last sector before actually writing the data onto the media.
If the drive detects an error after it returns a Good Status, the drive sets a Deferred Error (Error Code of sense data = 71h) and
a following command will be returned with Check Condition and the Contingent allegiance condition is established. Under the
Contingent allegiance condition all queued processes including commands from other initiators are suspended.
21.12 Automatic Rewrite/Reallocate
The target supports Auto and Recommended Reallocate for READ, WRITE, WRITE VERIFY, and VERIFY.
Automatic and Recommend Reallocate operate from within the read/write command. When an automatic reallocation occurs,
the read or write command takes longer to complete.
This operation is sometimes referred to as auto-reassignment due to its similarity to the operation performed by the reassign
command.
Following is a description of the target behavior for each setting of ARRE. ARRE setting affects all data errors. (No Sector
Found, Data Sync Byte Errors and Data ECC Errors.)
ARRE=1: An error site determined to need rewriting or reallocation during a read is automatically rewritten or reallo-
cated at the conclusion of the read and prior to the sending of the status. The site will be automatically
rewritten or reallocated only if the data has been successfully read.
ARRE=0: An error site determined to need rewriting or reassignment during a read is recommended for rewriting or
reassignment at the conclusion of the read.
The setting of the ARRE bit is checked and the target will automatically rewrite/reallocate or recommend rewrite/reassign for
the following commands.
• Read
• Write
For all other commands the ARRE setting is ignored and the target will not automatically rewrite/ reallocate or recommend
rewrite/reassign.