Fault Tolerance And Drive Failure; A Non-Fault-Tolerant (Raid 0) Logical Drive; A Raid 1 (Mirroring) Logical Drive - Compaq 219700-001 - ProLiant - 1500 Reference Manual

G-2 Recovering from Drive Failure
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 been
failed. If drive failures or repeated errors are suspected, Compaq recommends
that Drive Array Advanced Diagnostics be run 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.

A Non-Fault-Tolerant (RAID 0) Logical Drive

Can sustain no 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.

A 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.
Writer: Pamela King Project: SMART-2DH Array Controller Reference Guide Comments: 295469-002
File Name: N-APPG.DOC Last Saved On: 2/27/98 12:09 PM
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