Installation guide

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.