Technical information

HGST Ultrastar C15K600 Hard Disk Drive Specification
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20.4
Command Reordering
Command reordering is supported when enabled by the Queue Algorithm Modifier in mode page 0A (see 18.10.9
"Mode Page 0A (Control Mode Page Parameters)”.
20.5
Concurrent I/O Process
Concurrent commands are always allowed to execute concurrently with non-priority commands. A second priority
command received while a priority command is being executed is put at the head of the command queue.
- WRITE commands when another WRITE command is an active I/O process
- READ commands when another READ command is an active I/O process
When a concurrent command ends in CHECK CONDITION status, the QErr bit on the Mode Page 0Ah will
determine how other active I/O processes from the same initiator for that drive will be handled.
20.6
Write Cache
If the WCE (Write cache enable) bit is 1, the drive returns Good Status and closes the connection 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.
20.7
Automatic Rewrite/Reallocate
The target supports Auto Reallocate for READ, WRITE, WRITE VERIFY, and VERIFY.
Automatic Reallocate operates 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 LDPC Errors.)
ARRE=1: An error site determined to need rewriting or reallocation during a read is automatically rewritten or
reallocated 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: Behaves the same as ARRE=1.
The target will automatically rewrite/reallocate for the following commands.
- Read
- Verify
- Verify portion of Write and Verify
For all other commands the ARRE setting is ignored and the target will not automatically rewrite/ reallocate
Following is a description of the target behavior for each setting of AWRE. AWRE setting affects only No Sector
Found Errors on writes.
AWRE=1: An error site determined to need reassignment during a write is automatically reallocated at the
conclusion of the write and prior to sending the status. The site will be automatically reallocated only
if the write recovery succeeded at the conclusion of the write.
AWRE=0: Behaves the same as AWRE=1