Mylex DAC960PG, Installation Manual

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Functional Description
Manual No. 771971 2-19
When the controller detects a failure on a disk, it kills that disk by changing
its state to dead. A SCSI drive that is in the dead state does not participate in
any I/O activity. No commands are issued to dead drives.
Write-Only (WOL)
A SCSI drive is in a write-only state if it was in the process of being rebuilt,
that is ...
• During a RAID 1 rebuild process, data is copied from the mirrored
drive to the replacement drive.
• During a RAID 3, RAID 5, or RAID 0+1 rebuild, data is regenerated
via the XOR redundancy algorithm and written to the replacement
drive.
... and the rebuild was terminated abnormally before it completed.
Ready (RDY)
A SCSI disk drive may be identified by the DACCF utility as ready if it:
1. Is powered on
2. Is able to operate properly
3. Has not been defined as part of any drive group.
4. Has not been defined as a standby
Ready is not an actual drive state or command issued by the controller. The
drive will change from RDY to SBY (standby) when the configuration is
saved to memory.
Controlling Logical Unit States
The state of a logical unit on a DAC960PG can be ON-LINE, CRITICAL, or
OFF-LINE. Notice that the same term on-line is used for both physical
drives and logical units.
☛
Note
I/O operations can be performed only with logical
units that are either on-line or critical.
On-line
A logical unit is on-line if all of its participating physical drives are on-line.