Explanation
The SAN Volume Controller maintains a virtual medium error table for each MDisk. This table is a list of logical block addresses on the managed disk that contain data that is not valid and cannot be read. The virtual medium error table has a fixed length. This error event indicates that the system has attempted to add an entry to the table, but the attempt has failed because the table is already full.
There are two circumstances that will cause an entry to be added to the virtual medium error table:
- FlashCopy, data migration and mirrored VDisk synchronization operations copy data from one managed disk extent to another. If the source extent contains either a virtual medium error or the RAID controller reports a real medium error, the system creates a matching virtual medium error on the target extent.
- The mirrored VDisk validate and repair process has the option to create virtual medium errors on sectors that do not match on all VDisk copies. Normally zero, or very few, differences are expected; however, if the copies have been marked as synchronized inappropriately, then a large number of virtual medium errors could be created.
Action
Ensure that all higher priority errors are fixed before you attempt to resolve this error.
Determine whether the excessive number of virtual medium errors occurred due to a mirrored disk validate and repair operation that created errors for differences, or whether the errors were created due to a copy operation. Follow the corresponding option shown below.
- If the virtual medium errors occurred due to a mirrored disk validate and repair operation that created medium errors for differences, then also ensure that the VDisk copies had been fully synchronized prior to starting the operation.
If the copies had been synchronized, there should be only a few virtual medium errors created by the validate and repair operation. In this case, it might be possible to rewrite only the data that was not consistent on the copies using the local data recovery process.
If the copies had not been synchronized, it is likely that there are now a large number of medium errors on all of the VDisk copies. Even if the virtual medium errors are expected to be only for blocks that have never been written, it is important to clear the virtual medium errors to avoid inhibition of other operations. To recover the data for all of these virtual medium errors it is likely that the VDisk will have to be recovered from a backup using a process that rewrites all of the VDisk's sectors.
- If the virtual medium errors have been created by a copy operation, it is best practice to correct any medium errors on the source VDisk and to not propagate the medium errors to copies of the VDisk. Fixing higher priority errors in the error log would have corrected the medium error on the source VDisk. Once the medium errors have been fixed, you must run the copy operation again to clear the virtual medium errors from the target VDisk. It might be necessary to repeat a sequence of copy operations if copies have been made of already copied medium errors.
An alternative that does not address the root cause is to delete VDisks on the target managed disk that have the virtual medium errors. This VDisk deletion reduces the number of virtual medium error entries in the MDisk table. Migrating the VDisk to a different managed disk will also delete entries in the MDisk table, but will create more entries on the MDisk table of the MDisk to which the VDisk is migrated.
Possible Cause-FRUs or other: