Tuesday, 2 October 2012

Managing Duplicate To Tape Jobs

When backups are done to tapes, it is normal to maximise the use of the tape space and thus minimising the number of tape used.  To achieve this objective, the following have to be in-place
1) The first job that writes to the tape overwrites it and the rest of the jobs will append to the tape.
2) All the jobs target the tape drive, rather than the tape library.  This is to prevent the jobs from using another tape drive and consequently another tape if there is more than one tape drive in the library.
3) All the jobs target the same media set, so that the same tape will be used.  The AP of this media set have to be set long enough so that the last job can append to this tape.
4) If the "append, otherwise overwrite" option is used, the jobs does not overlap.  See my article for an explanation why this is necessary.
These conditions can be meet quite easily if the number of jobs are small and the start time of the jobs can be set.
If you are doing B2D2T and there are many jobs, it is not easy to schedule the B2T jobs because they are normally set to start as soon as the B2D jobs end.

With BE 2012, one way to achieve to achieve the objective of maximising the use of tape space with B2T jobs is not to define any B2T jobs.  You wait for all the B2D jobs to end.  Go to the Storage tab, select all the backup sets that you want to duplicate to tape and duplicate them all at one go.  See my blog
The disadvantage of this method is that you have to do setup the duplicate job manually each time you want to do the B2T duplication and apparently, there is a limit of 63 backup sets that you can select at one time.

An automated way of doing the B2T duplication is
1) Put all the B2T jobs on hold.
2) Get the list of B2T jobs by running this BEMCLI cmdlet
Get-BEJob -Jobtype Duplicate > duplicate-jobs.txt
3) Edit duplicate-jobs.txt and arrange the jobs in the order which they will run.
4) For the first job on the list, the job property should specify Overwrite
5) Download the Chain-BEJobs script
6) Use the Chain-BEJobs script to run the list of jobs in the duplicate-jobs.txt file.  You can either schedule the script using Windows Scheduler to run after all the B2D jobs are done or use the script as a pre-/post-command for the last B2D job.
If you are also chaining your B2D jobs, then you can just append the list of B2T jobs to your list of B2D jobs.  For example,
B2D Job 1
B2D Job 10
B2T Job 1
B2T Job 10

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