2008-05-21 08:40 AM
I believe i may have posted this same questions here earlier and i apologize if i have.
The problem i am experiencing is that when an image expires in Netbackup it is not deleted off the Virtual tape. With our VTL being about 400% over allocated this becomes a problem. The only solution i have come up with is to do a long erase on tapes once they are sent back to the scratch pool in netbackup.
I have heard that some VTLs out there have a solution to this and it's called something like "Tabs". Tabs are left on the virtual tape at the end of each image and the vtl is aware when netbackup expires an image and goes to the "Tab" and deletes the image.
Anyone know of a solution to this for NetApp VTLs?
Is this a problem NetApp is aware of?
I have also posted a message on the Symantec forums.
2008-06-02 07:46 AM
Even though NetBackup (or any backup software) expires images out of its catalog, the data on the actual tape does not get erased. This is true for both virtual and physical tapes.
Physical tapes that are in your library still have data on them.. even though NetBackup marks those tapes as 'scratch'.
In the VTL, that means that the virtual tapes are still taking up disk space even though NetBackup won't go back to those tapes to get data. Since those tapes are considered 'scratch' it means that we can overwrite the data on the tapes and not worried about NetBackup wanting to use the tapes (similar to a brand new tape... no recovery will be requested from the tape)
On a physical tape if you overwrite the first byte of a tape, the rest of the tape becomes invalid (only that first byte is now valid). Similarly on a virtual tape, if you overwrite the first byte the rest of the virtual tape is invalid... which also means the VTL will free the associated disk space.
The solution to freeing up disk space on virtual tapes that contain data (but are no longer needed by the backup application) is to re-write the first byte of the tape. This can easily be accomplished by a simple script that determines which scratch tapes are in NetBackup and then mounts and writes a new byte to the beginning of the tape.
2008-06-02 09:30 AM
Andy, the problem I have is that some of the tapes were never making it to the scratch pool and they were not involved in an offsite rotation because they only did differential/incremental backups so they never made it to the shadow pool either.
Chuck, Thanks for taking time on the phone the other day. I have since realized that to help elevate the problem i can periodically mark the tapes that never get to scratch or the shadow pool as read only. Once the images on them expire they will be moved to scratch and erased with a script. This is a rather manual process but should be very effective. I haven't applied this yet but i don't see why it wouldnt work.