User guide

F-2 Compaq StorageWorks RAID Array 4100 User Guide
■ Compaq Insight Manager can detect failed drives remotely across a
network.
Problems such as reduced system performance or disk errors reported by the
operating system do not necessarily imply that a drive has or has not failed. If
drive failures or repeated errors are suspected, Compaq recommends running
the Array Diagnostic Utility on the system.
Fault Tolerance and Drive Failure
In the event of a drive failure, the condition of the logical drive will vary
depending upon the fault-tolerance method used. Since a single array of
physical drives can contain multiple logical drives with differing
fault-tolerance methods, conditions of each logical drive on the same array are
not necessarily the same. At any one time, if more drives are failed than the
fault-tolerance mode allows, fault tolerance is referred to as being
compromised and the condition of the logical drive can be referred to as
“failed.” If a logical volume is failed, all requests from the operating system
will be rejected with unrecoverable errors.
Non-Fault-Tolerant (RAID 0) Logical Drive
Non-Fault-Tolerant (RAID 0) Logical Drives cannot sustain drive failures. If
any physical drive in the array is failed, the condition of all non-fault-tolerant
logical drives in the same array will also be “failed.” This is because data is
striped across all drives in the array.
RAID 1 (Mirroring) Logical Drive
■ Can sustain multiple drive failures as long as failed drives are not
mirrored to one another.
■ Will be in a failed condition if any two failed drives are mirrored to one
another.
■ Will be in a “regenerating” condition if at least one drive is failed, and
no failed drives are mirrored to one another.
■ Will be in a “rebuilding” condition if a previously failed drive has been
replaced and the replacement drive is rebuilding. The volume may also
be in a rebuilding condition following a drive failure if a spare drive was
previously assigned and is rebuilding.