Why does backup require 2x the amount of space as the drive I'm backing up? RRS feed

  • Question

  • I have a hdd internal on my machine that has 931 gb capacity, with 369 gb of free space. Honestly a lot of it is cruft I never clean up (games I don't play, stuff I downloaded I don't look at) that I'm trying to back up to a 931 gb external ESATA (or usb 2) hdd - this disk is completely empty, I've never had a backup succeed or even start because it says there isn't enough space. Granted I'm no mathematician, but from what I see it should be able to do a first full backup with zero compression and still have 396 gigs free.

    However I get an error that I don't have enough disk space and that I need to free up 358.7 gb - which means it intends to backup about 1289 gb of data...

    Is it backing up every file 3-4 times? I know when I was a TSM admin (tivoli storage management) compression usually meant on most data that the backup would actually be *smaller* than the machines contents - at least initially.

    Anyone have any idea what is going on?
    Monday, September 7, 2009 10:03 PM


All replies

  • Are you having this issue with One Care backup?
    Jim - MVP Windows Live - Forum Moderator - Live One Care - Live Mesh - Microsoft Security Essentials
    Monday, September 7, 2009 10:31 PM
  • Yes - on Vista 64 Ultimate.
    Monday, September 7, 2009 10:43 PM
  • I suggest contacting support for help with this as your numbers would seem to indicate that you've got plenty of free space to perform the backup. OneCare only backs up data per the plan settings you've selected, so the total backup should be conisderably less than the 600 Gigs that you've used on the internal drive. 

    How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90


    Microsoft MVP Windows Live / Windows Live OneCare, Live Mesh, & MS Security Essentials Forums Moderator
    Tuesday, September 8, 2009 12:33 AM