Disk Drive Health Check in NonStop Systems

Disk Drive Health Check
This procedure describes how to perform a health check (scan) for a NonStop disk drive that is
to be the sole member of a mirrored volume to be left online as a data source during
mirror-splitting operations such as disk replacements, online disk capacity upgrades, and
migratory REVIVEs.
Notes and Cautions
CAUTION:
• Some versions of FCHECK have a defect that could cause media errors to go undetected.
For G-series, use T9208ABQ or a subsequent SPR. For H-series, use T9208ABP or a subsequent
SPR.
• Note that the T9053AQD prerequisite for T9208ABQ can be ignored for online disk capacity
upgrades. For migratory REVIVEs, both T9208ABQ and T9053AQD (or a subsequent SPR)
should be installed in order to ensure that all SQL/MP tables are included in the space
estimate and to fix several migratory REVIVE defects.
• Disk media errors can be intermittent. Even though a drive has been scanned successfully,
there still is the potential for a media error to arise during the subsequent REVIVE operation.
NOTE:
• During a mirrored pair disk replacement, online disk upgrade, or migratory REVIVE, there
are periods where the disk volume is in a non-fault-tolerant mode because one of the pair
of drives is being used as the target for the REVIVE operation and does not contain a complete
copy of the data. Because of this, it is important to perform steps to ensure that the drive
that is to be the source of each REVIVE operation has been scanned as a health check so no
data will be lost due to media or checksum errors on that drive. FCHECK is the utility used
to do the scanning and repairing. If one of the drives being scanned has a valid checksum
and the other drive has an invalid checksum, the –SCAN option automatically copies the
data with the valid checksum to the drive with the invalid checksum. If Automatic Sector
Reallocation is enabled, running FCHECK –SCAN causes every in-use sector on both halves
of a logical disk to be read. The DP2 driver automatically reports any media errors
encountered during this scan, and the reallocation recovers the data from the good copy.
As a result, media errors are reported and automatically corrected, if possible.
• For all migratory REVIVEs and for online disk capacity upgrades being done on a volume
that does not have CAPACITYMISMATCH set, the source drive is automatically placed in a
hard down state at the end of the first REVIVE. Because of this, there is no opportunity to
perform a data comparison between the two drives or otherwise health-check the
newly-REVIVEd drive before it becomes the source for the second REVIVE. In these cases,
it is recommended that the customer perform health checks on that drive as described below
prior to beginning the mirror-splitting procedure and clearly label the drive as having been
scanned. This recommendation is particularly important if the first target drive is taken from
an existing system rather than coming from HP as either a new drive or a replacement drive.
Drives coming from HP already have been fully scanned.
• CAPACITYMISMATCH is supported in G06.29 and later G-series RVUs, all H-series RVUs,
and RVUs prior to G06.29 that have SPR T9753G07^AGB or a subsequent SPR installed.
4 Disk Drive Health Check