HP File System Extender (FSE) manual Media Pool

actual layout of the remigrated data on FSE media differs from the original data layout on the unreadable medium.

Figure 23 Recreating a copy of damaged migrated data

Media Pool 2

F2 F3 F4'

Media Pool 4

F4'' F5 F6

F3 F4 F5' F5'' F6 F3 F4 F5'

F5''

If alternative migrated copies of the unrecallable data exist in both tape and disk media pools, the redundant copy is recreated from the data stored in the disk media pool. By using the disk media pool, as many FSE drives as possible remain available for other FSE processes, such as migration and recall. You can define the total number of drives that can be simultaneously used for redundant copy recreation (for example, when several media are damaged) with the FSE partition configuration variable SystemMaxNumDrivesMaint. Note that this variable affects all types of maintenance jobs.

NOTE: The redundant copy recreation process operates on a “best-effort” basis. It processes all file generations that can be copied from an alternative location on FSE media and skips the files for which the copying cannot be done. The process recreates only the generations that were migrated to the unusable medium.

In cases where no alternative migrated copies of the unreadable data exist, a warning (the unreadable data belongs to a non-latest file generation) or an error (the unreadable data belongs to the latest file generation) is reported to the FSE error log for each file that cannot be recreated.

NOTE: You are not restricted to creating a redundant copy of an FSE medium only when the medium is already damaged and has the status set to unusable. You can also perform this action with a worn-out medium that has the status set to unreliable and even with a medium that can be read and written to. This way you avoid losing a migrated data copy before the problem arises or becomes more severe.

After creating a redundant copy of an unreliable or a “good” (usable) medium, two valid (readable) data copies exist in the same FSE media pool. Note that you cannot have more than two valid copies of the same data in the same media pool.

CAUTION: If you use the command fsemedium --copy-contentswith a “good” (usable) medium that has empty or open volumes with free space, the redundant copy recreation process may start creating the redundant copy on the same medium. In this case, the newly created additional copy does not increase data safety.

114 Managing media