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WHS shares backup storage oddity RRS feed

  • Question

  • Hello, sort of newbie question here:

    I have connected an external USB drive (300 GByte) to my WHS and
    using it as backup media for the WHS shares.

    I have backed up my shares 5 - 6 times.

    But the strange thing is:
    When I view properties on my USB drive (F:), it says 230 GByte used, but
    if I view properties on the individual backup directories on the USB
    it adds up to well over 300 GByte, more like 700 GBytes.

    How does WHS store backups of my shares ?
    The files does not seem to be compressed.

    Is is some NTFS feature I'm not aware of ?

    What backup directories on my USB can I delete
    without loosing my data ?

    thanks in advance

    Per

    Friday, March 13, 2009 7:56 AM

Answers

  • Hi Per,
    this is normal, since the WHS integrated server backup uses tombstones for unchanged files on the backup disk. So it ensures that each file is only one timer there, but reachable directly from each of the subsequent backups.
    More storage efficiency - but Explorer can not distinguish between tombstones and real files, so the properties of the tombstones are adding up in the Properties dialog with the full file size for each backup.
    Best greetings from Germany
    Olaf
    Friday, March 13, 2009 9:01 AM
    Moderator
  • Per, the answer to your question about deleting a folder is that yes, it's safe to delete a folder in one backup of your shares even if it contains a hard link that points to a file in a different backup. The way hard links handle this is to maintain a count of the number of references to a file, and increment/decrement that count as additional links are created or deleted. When the number of references drops to 0 the file itself is deleted.
    I'm not on the WHS team, I just post a lot. :)
    Friday, March 13, 2009 4:59 PM
    Moderator

All replies

  • Hi Per,
    this is normal, since the WHS integrated server backup uses tombstones for unchanged files on the backup disk. So it ensures that each file is only one timer there, but reachable directly from each of the subsequent backups.
    More storage efficiency - but Explorer can not distinguish between tombstones and real files, so the properties of the tombstones are adding up in the Properties dialog with the full file size for each backup.
    Best greetings from Germany
    Olaf
    Friday, March 13, 2009 9:01 AM
    Moderator
  • Thank you Olaf, for your explanation.

    Still though, is it safe to me to delete a directory
    containing a backup'ed file existing in another backup directory,
    without loosing that file ?

    I mean, since explorer delete does not understand (I assume) the tombstone files ?

    In a nutshell, how do I manage my WHS share backup database ?


    thankful for any insight

    Per
    Friday, March 13, 2009 9:27 AM
  • Olaf Engelke said:

    this is normal, since the WHS integrated server backup uses tombstones for unchanged files on the backup disk.

    Not quite. The server backup tool uses NTFS hard links. A hard link is effectively a pointer or alternate name for a file. It uses the same MFT entry that the original file does. A Windows Home Server "tombstone" is an NTFS reparse point. A reparse point tells the operating system to call a file system filter driver to handle the actual file. This filter driver might do any number of things, and it can store data in the reparse point, so the reparse point is really a file of sorts on it's own. 




    I'm not on the WHS team, I just post a lot. :)
    Friday, March 13, 2009 4:57 PM
    Moderator
  • Per, the answer to your question about deleting a folder is that yes, it's safe to delete a folder in one backup of your shares even if it contains a hard link that points to a file in a different backup. The way hard links handle this is to maintain a count of the number of references to a file, and increment/decrement that count as additional links are created or deleted. When the number of references drops to 0 the file itself is deleted.
    I'm not on the WHS team, I just post a lot. :)
    Friday, March 13, 2009 4:59 PM
    Moderator
  • Thanks Ken,

    now I can purge my USB disk after your explanation.

    Funny thing, I was discussing this issue with my colleges
    during lunch, and we were guessing what was going on.

    Me, with my (long way back) UNIX background guessed it could something
    similar to UNIX hard links. Then I didn't know about NTFS hard
    links until you told me.

    thanks

    Per

    Friday, March 13, 2009 6:52 PM