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    Not really an expert on backups... but if I recall correctly, the OS keeps track of what has been backed up by a certain file attribute.  Once backed up, the attribute is changed so the OS knows not to add to the next incremental backup.  Now, here's the problem.  The very first backup of my client PC began while I was still using the computer.  I wasn't quite done, so i cancelled the backup.  All subsequent backups have been made.  My concern is that since the first backup had actually started, can I be sure that ALL of my files are backed up?  If the file attributes were changed, my client wouldn't know to backup those files the next time.  On a more general note, when WHS deletes old backups (automatically managing backups), how is that communicated to the client so that subsequent backups are complete?

     

    I know this is kind of a convoluted question, I just want to make sure the backups of my client are absolutely complete.

    Sunday, March 16, 2008 3:45 AM

Answers

  •  Jerryrigged wrote:

     

    Actually, let me state this question a different way... Lets say I were to go onto my server today and delete all of the backups of my client.  On my client computer, all files that have already been backed-up will show an attribute that they've already been backed-up.  Now, I go to do a new backup... my client will want to only backup the files that have changed since yesterday.  Why or how would my client know to re-do a full backup?

     

    Like I said before WHS does NOT set the archive bit on backed up files or folders. It's only doing a backup of changed clusters on a specific partition. The clusters to backup are determined by comparing the contents of the most  recent backup of the partition with a new shadow copy of the partition.

     

    So:

     

    1.  if no backups are present for a particular partition the whole partition will be backed up.

    2. If you change one or two words in a large text file and save the file it's very likely that only a few clusters (storage units) on the disk are actually changed. WHS will only backup the changed clusters and NOT the whole file.

     

    If you know little about the way shadow copies work and / or how files are actually stored on disk, I can imagine it's difficult to understand this concept. The best thing to do would be read the WHS documentation on this subject: Home Computer Backup. This explains most of this in a comprehensive way.

    Monday, March 17, 2008 9:59 PM
    Moderator

All replies

  • I'm not entirely sure how it works, but I'll take a crack at it.  From what I understand, WHS actually compares files when it's doing backups.  If they files are different, it backs them up.  Either way, I'm sure all your files are backed up correctly.  I've used my laptop a few times while backing up and everything seems just fine. 
    Sunday, March 16, 2008 4:23 AM
  • Cancelling the backup should be no problem. However there's also no reason to cancel a backup when you're working on the computer. WHS does the backup of each volume based on a shadow copy of that volume, so there's no problem when you use the machine during backup. If you want to be really sure if the backup's are OK just try opening one or more recent backups

     

    In the technical brief Home Computer Backup (page 9) you can read some more details about the way WHS backup works.

     

    EDIT: AFAIK WHS does not compare the actual files, it only looks for changed clusters based on the volume shadow copy

    Sunday, March 16, 2008 4:27 AM
    Moderator
  •  

    There was something I read in one of the tech briefs that said performance would slow down considerably if the computer was backing up.  And, since I was still doing some server configurations at the time, I CANCELLED the backup.  If I hadn't cancelled it, I would probably feel confident once it was done.  I was just thinking that the next day, when it did an un-interupted backup, IT SHOULD HAVE BEEN A COMPLETE BACKUP... just not sure that it was - since some file attributes on day one may have been changed.

     

     

    Sunday, March 16, 2008 4:37 AM
  •  

    Actually, let me state this question a different way... Lets say I were to go onto my server today and delete all of the backups of my client.  On my client computer, all files that have already been backed-up will show an attribute that they've already been backed-up.  Now, I go to do a new backup... my client will want to only backup the files that have changed since yesterday.  Why or how would my client know to re-do a full backup?

     

    Sunday, March 16, 2008 4:41 AM
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    If you delete all the backups, the next backup that runs will be a full backup. If you ever need to restore a PC, and you select the latest backup, all the data the way it was on that particular day is how your PC will be restored.
    Sunday, March 16, 2008 7:47 AM
    Moderator
  •  Jerryrigged wrote:

     

    Actually, let me state this question a different way... Lets say I were to go onto my server today and delete all of the backups of my client.  On my client computer, all files that have already been backed-up will show an attribute that they've already been backed-up.  Now, I go to do a new backup... my client will want to only backup the files that have changed since yesterday.  Why or how would my client know to re-do a full backup?

     

    Like I said before WHS does NOT set the archive bit on backed up files or folders. It's only doing a backup of changed clusters on a specific partition. The clusters to backup are determined by comparing the contents of the most  recent backup of the partition with a new shadow copy of the partition.

     

    So:

     

    1.  if no backups are present for a particular partition the whole partition will be backed up.

    2. If you change one or two words in a large text file and save the file it's very likely that only a few clusters (storage units) on the disk are actually changed. WHS will only backup the changed clusters and NOT the whole file.

     

    If you know little about the way shadow copies work and / or how files are actually stored on disk, I can imagine it's difficult to understand this concept. The best thing to do would be read the WHS documentation on this subject: Home Computer Backup. This explains most of this in a comprehensive way.

    Monday, March 17, 2008 9:59 PM
    Moderator