Array States - Dot Hill Systems RAIDCore User Manual

Array States

Within the management applications, an array is a logical device that can exist in one of three states: Normal,
Critical, or Offline.
• In RAIDConsole, these states display in the Array List section in a column named State.
• Within the bcadm Command Line tool, these states also display in a column named State.
The array states are defined in the following table.
Table 7 Array States
State
Normal
Critical
Offline
Whether an array is marked as Critical or Offline depends upon what RAID level it is and how many disks
within the array have failed. Note the changes in state in the following table.
Table 8 Failure States by RAID Level
RAID Level
RAID 1, RAID 5
RAID 1n, RAID 10,
RAID 10n, or RAID 50 (RAID
levels with multiple redundancies)
Volume and RAID 0
RAID 1 and RAID 5
(redundant arrays)
RAID 1n, RAID 10, RAID 10n
(RAID levels with multiple
redundancies)
RAID 50
(RAID levels with multiple
redundancies)
For example, RAID 50 is a stripe of RAID 5 sets. If a RAID 50 set contains three RAID 5 sets, each RAID 5 set
can have up to one disk failure. The RAID 50 array state shows as Critical. If a third disk fails, the state of the
RAID 50 array changes to Offline. Or, if two disks fail on one of the RAID 5 sets, the state of the RAID 50
array changes to Offline.
More than one array can be created using the same set of disks. If a disk is disconnected that belongs to more
than one array, only the arrays that try to access the disk and receive I/O errors report the failure. For example:
there are two arrays, both of which are RAID 5 sets, and both use disk 4. If a system being used by array 1
receives an I/O error when trying to communicate with disk 4, the state of array 1 changes to Critical. However,
the state of array 2 using disk 4 does not change to Critical until an I/O error is reported. If systems using array
1 are not communicating with failed disk 4, the state of array 1 still displays as Normal.
If a rescan of all channels is performed after disconnecting a disk, the state of every array using the missing
disk changes from Normal to either the Critical or Offline, depending on the RAID level.
See Rescanning Disks for Changes in State
outcomes when doing so.
Description
The Normal state is displayed when everything is functioning correctly.
The Critical state is displayed when the array is no longer redundant (fault tolerant)
because of one or more disk failures. Arrays can still be read and written to, but the data
is no longer protected should another disk fail.
The Offline state is displayed when arrays cannot be read or written to because of one or
more disk failures.
This Failure State...
Critical
Critical
Offline
Offline
Offline
Offline
on page 29 for a discussion of when to rescan disks and the
Is Displayed Whenever...
A single disk fails.
A single disk fails in any one of those sets.
A single disk fails.
Two or more disks fail.
All disks in a set fail.
Two or more disks fail.
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