Undo-jobs and Mount Points

Coordinating Undo-jobs with Other Operations

When an undo-job is run, the BCV units will be unmounted. For jobs such as backups, the undo-job is planned to occur after the backup is done and the BCV units are no longer needed. For jobs such as system testing or migration, running the undo-job at the wrong time could interfere with the other operations.

 

Coordinating Undo-jobs after a Partial Job Completion

When a job with multiple BCV mountings is stopped short of normal completion, it is possible that only some of the BCV units will have been mounted. Only the mounted BCV units will be visible to the host's operating system and application programs. When the undo-job is run, EVM will unmount the mounted BCV units.

 

EVM Job Mounting Sequence

When a job includes more than one unit to replicate and mount, the sequence of events is:

  1. Replicate all units.

  2. Execute the Application I/O Handler pre-split command or batch file.

  3. Split all BCV units, in order by unit name (e.g. units D1, D2, D3).

  4. Execute the Application I/O Handler post-split command or batch file.

  5. Mount all BCV units, in order by unit name.

 

EVM Undo-job Unmounting Sequence

When an undo-job is run, the process is reversed. The sequence is:

  1. Unmount all BCVs, in order by unit name.

  2. Return all source units to their original configurations, in reverse order by unit name (e.g. units D3, D2, D1) and return unused disks to the pool of free disks.