Installation guide

Glossary
Manual No. 775020 G-3
When a replacement drive becomes available, the system operator can
remove the failed disk drive, install a new disk drive, and instruct the
controller to “rebuild” the data on the new drive, all without interrupting
system operations.
Once the rebuild is complete, the controller will be brought back into a fault
tolerant state.
Logical Drive States
The state of a logical (system) drive can be either ONLINE, CRITICAL, or
OFFLINE. Notice that the same term “online” is used for both physical and
logical drives.
Online: A Logical Drive is in an “online” state if...
All of its participating SCSI drives are “online.”
Critical: A Logical Drive is in a “critical” state if...
It has been configured at RAID level 1, 3, 5, or 0+1; and
One (and only one) of its SCSI drives is not “online.”
A logical drive is considered “critical” because any failure of another of its
SCSI drives may result in a loss of data.
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Note
I/O operation can only be performed with system
drives that are online or critical.
Offline: A Logical Drive is in an “offline” state if...
No data can be read from it or written to it.
System commands issued to offline logical drives are returned with an error
status: no operations can be performed on offline logical drives. A logical
drive can be “offline” under one of two situations described below:
• It is configured with a redundant RAID level (1, 3, 5, or 0+1), and two
or more of its SCSI drives are not “online”; or
• It is configured at RAID level 0, JBOD, or in a spanned set, and one or
more of its SCSI drives are not “online.”