Automatic Data Recovery (Rebuild) - HPE Smart Array P240nr User Manual

•
Confirm that the replacement drive is of the same type as the degraded drive (either SAS or SATA
and either hard drive or solid state drive).
•
Use replacement drives that have a capacity equal to or larger than the capacity of the smallest drive
in the array. The controller immediately fails drives that have insufficient capacity.
In systems that use external data storage, be sure that the server is the first unit to be powered down and
the last unit to be powered up. Taking this precaution ensures that the system does not, erroneously,
mark the drives as failed when the server is powered up.
In some situations, you can replace more than one drive at a time without data loss. For example:
•
In RAID 1 configurations, drives are mirrored in pairs. You can replace two drives simultaneously if
they are not mirrored to other removed or failed drives.
•
In RAID 10 configurations, drives are mirrored in pairs. You can replace several drives
simultaneously if they are not mirrored to other removed or failed drives.
•
In RAID 50 configurations, drives are arranged in parity groups. You can replace several drives
simultaneously, if the drives belong to different parity groups. If two drives belong to the same parity
group, replace those drives one at a time.
•
In RAID 6 configurations, you can replace any two drives simultaneously.
•
In RAID 60 configurations, drives are arranged in parity groups. You can replace several drives
simultaneously, if no more than two of the drives being replaced belong to the same parity group.
•
In RAID 1 (ADM) and RAID 10 (ADM) configurations, drives are mirrored in sets of three. You can
replace up to two drives per set simultaneously.
To remove more drives from an array than the fault tolerance method can support, follow the previous
guidelines for removing several drives simultaneously, and then wait until rebuild is complete (as
indicated by the drive LEDs) before removing additional drives.
However, if fault tolerance has been compromised, and you must replace more drives than the fault
tolerance method can support, delay drive replacement until after you attempt to recover the data (refer to
"Recovering from compromised fault

Automatic data recovery (rebuild)

When you replace a drive in an array, the controller uses the fault-tolerance information on the remaining
drives in the array to reconstruct the missing data (the data that was originally on the replaced drive) and
then write the data to the replacement drive. This process is called automatic data recovery or rebuild. If
fault tolerance is compromised, the controller cannot reconstruct the data, and the data is likely lost
permanently.
If another drive in the array fails while fault tolerance is unavailable during rebuild, a fatal system error can
occur, and all data on the array can be lost. However, failure of another drive does not always lead to a
fatal system error in the following exceptional cases:
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Failure after activation of a spare drive
•
Failure of a drive that is not mirrored to any other failed drives in the following configurations:
RAID 1
o
RAID 10
o
RAID 1 (ADM)
o
RAID 10 (ADM)
o
•
Failure of a second drive in a RAID 50 or RAID 60 configuration if the two failed drives are in different
parity groups
•
Failure of a second drive in a RAID 6 configuration
tolerance" on page 22).
Drive procedures 23