Bad Block Errors - IBM Storwize V7000 Unified Series Problem Determination Manual

The allocates volumes from the extents that are on the managed disks (MDisks).
The MDisk can be a volume on an external storage controller or a RAID array that
is created from internal drives. In either case, depending on the RAID level used,
there is normally protection against a read error on a single drive. However, it is
still possible to get a medium error on a read request if multiple drives have errors
or if the drives are rebuilding or are offline due to other issues.
The provides migration facilities to move a volume from one underlying set of
physical storage to another or to replicate a volume that uses FlashCopy or Metro
Mirror or Global Mirror. In all these cases, the migrated volume or the replicated
volume returns a medium error to the host when the logical block address on the
original volume is read. The system maintains tables of bad blocks to record where
the logical block addresses that cannot be read are. These tables are associated with
the MDisks that are providing storage for the volumes.
The dumpmdiskbadblocks command and the dumpallmdiskbadblocks command are
available to query the location of bad blocks.
It is possible that the tables that are used to record bad block locations can fill up.
The table can fill either on an MDisk or on the system as a whole. If a table does
fill up, the migration or replication that was creating the bad block fails because it
was not possible to create an exact image of the source volume.
The system creates alerts in the event log for the following situations:
v When it detects medium errors and creates a bad block
v When the bad block tables fill up
The following errors are identified:
The recommended actions for these alerts guide you in correcting the situation.
Bad blocks are cleared by deallocating the volume disk extent by deleting the
volume or by issuing write I/O to the block. It is good practice to correct bad
blocks as soon as they are detected. This action prevents the bad block from being
propagated when the volume is replicated or migrated. It is possible, however, for
the bad block to be on part of the volume that is not used by the application. For
example, it can be in part of a database that has not been initialized. These bad
blocks are corrected when the application writes data to these areas. Before the
correction happens, the bad block records continue to use up the available bad
block space.
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Storwize V7000 Unified: Problem Determination Guide Version
Table 40. Bad block errors
Error code
1840
1226
1225
Description
The managed disk has bad blocks.
The system has failed to create a bad block
because the MDisk already has the
maximum number of allowed bad blocks.
The system has failed to create a bad block
because the system already has the
maximum number of allowed bad blocks.