Can SQL Backup pre-allocate disk space

  • This may fall into a category of who-cares or why-bother...and I accept that.

    I notice that the disk I use for backups (dedicated seperate physical drive) becomes excessively fragmented. I am guessing that SQL initially opens a farily small file and extends as necessary for the backup. I am curious if there is a way inside SQL or outside SQL with some disk characteristic, that would allow me to specify an intial size of the file (pre-allocate) so that the files dont become so fragmented.

    Iam currently mitigating the problem each day at end-of-day by copying the file. The copied file is not fragmented (clearly its easier for the OS when it knows at the outset how big the file will be. Then I delete the original fragmented file. This is successful, but not very sexy.

    Any ideas?

  • You are correct and I am not aware of anything that would preallocate space but do wonder what your motives are if you have a dedicated disk? You will be shipping them off to tape anyway and I assume these things get done out of hours in any case?

  • It's a philosophical "its the right thing to do" issue for me, that I would like to correct IF there was an appropriate solution. I keep 3-5 days of backups online, and the files end up with a few thousand extents.

    There is no other use of this disk...so no performance consequence. The nightly copy/delete resolves the issue...but Id prefer to fix the "problem", rather than fix the "symtpom".

    Thanks for your reply!

  • I wish I had time to worry about such things. 🙂 I would just accept it and add value elsewhere, cost vs benefit and all that.

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