Question on backup size and validation:

Discussion in 'Acronis True Image Product Line' started by Goober, Mar 1, 2008.

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  1. Goober

    Goober Registered Member

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    Ran a full backup up this morning. Went quickly and smoothly.

    Backup file size was 13.2 gigs but the data on C is actually 17.4 gigs. Is the diff due to compression?

    Ran a validation, A tab came up and said operation was successful or something to that effect. I suppose this means everything was OK otherwise I would have been alerted, correct?

    Thanks for the help!
     
  2. jorge7

    jorge7 Registered Member

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    According to the description in ATI, the "normal" compression setting reduces the total size approximately 55%, but this varies depending on compressibility of your files. What you report sounds reasonable.

    To sharpen your second question further, I have always assumed, without evidence, that the verification step does a bit by bit comparison of the backup with the actual files on the disk, and reports if even one bit is different. I assumed that the report of a successful backup with verification means that every single bit matches. Can someone from Acronis confirm or correct this?
     
  3. Goober

    Goober Registered Member

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    I really believe, in this case, the

    lack of evidence is NOT evidence in and of itself.
     
  4. MudCrab

    MudCrab Imaging Specialist

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    TI does not compare the created image with the files on the disk. It reads back the image file and checks it for errors. This allows you to Validate the image at any time without needing access to the original files.

    seekforever has posted many times how this works:
    If you have only Validated your backup image while in Windows, you really should (at the very least) boot to the TI CD and make sure you can Validate it from there. If disaster strikes it won't help if you can't successfully read your backup image.
     
  5. Goober

    Goober Registered Member

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    Seems logical but my CD is yet to arrive.

    Thanks for the tip.
     
  6. CorruptedSanity

    CorruptedSanity Registered Member

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    How do I do that without the TI CD? I bought my copy online and have no boot CD.
    I created a bootable media (iso image) to an external drive.
     
  7. MudCrab

    MudCrab Imaging Specialist

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    You can use Acronis Media Builder to create the TI CD or to create an ISO and burn than to a CD using an ISO capable burning program (like Nero).

    You can also create a bootable USB flashdrive and boot from that. A bootable USB hard drive can also be used, though not created directly with Media Builder.

    The main thing is to at least Validate the image using the environment which will be used to do a restore.
     
  8. jonyjoe81

    jonyjoe81 Registered Member

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    If the image backup completes with no errors then it's good. Doing a verification is a waste of time. I have never done a verification yet but have done numerous restorations and they all work with all the data transfered.

    I have full confidence that my backups are good even though I never verify them. If I want to test my backup, I just mount it and open up some folders to see if they look ok.

    If on the other hand when the backup completes, there is a message that says"backup completed with errors", then that would be something to look into.
     
  9. CorruptedSanity

    CorruptedSanity Registered Member

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    MudCrab, I really dont want to buy nero, nor do I want to use a cracked version. Is there no other way to create a bootable CD?

    jony, so far my only guaranteed way to check a backup was to restore to it after creation. You also mention a good but not really full way. To mount it and randomly check files.
     
  10. MudCrab

    MudCrab Imaging Specialist

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    I know there are differing opinions on whether or not Validating images is worth the time or even if it means anything. Corrupt images will usually mount, however corrupt images will not Validate or Restore.

    In this case, the user did not even have the TI CD, did not boot from it and did not check to see if TI sees the drives and can access the backup image. In situations like that, it's best to at least boot to the TI CD and Validate the image. This will let you know that TI can see your drives okay and that it can correctly read the image file.

    Some users are not comfortable testing a backup by restoring it to their working system or they don't have a spare hard drive on which to test it.

    Never doing a Validation or a Restore from the restore media is a very bad idea. You can easily fall into the trap of thinking it will work because it works in Windows and then find out it doesn't when you really need it.

    For people that backup less frequently (once a week, monthly, etc.), I still recommend doing a Validation on backup images. I've had cases where the image was saved to a hard drive with a bad sector. This image would not have been detected as corrupt had a Validation not been run. Having an image successfully pass a Validation does not guarantee it will still be good six months later, but it does mean it's good right now which is the best you can do.
     
  11. MudCrab

    MudCrab Imaging Specialist

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    Does Acronis Media Builder not work correctly on your computer? It should have been installed with TI.

    There are plenty of free ISO capable programs available to burn CDs. For example, here. A Google serach will find more.
     
  12. shieber

    shieber Registered Member

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    When aTI creates a backup, it creates a checksum number every few thousand bytes and embeds the checksum numbers in the file -- which, btw, is why a backup of already compressed files -such as jpegs or mp3s -- can take up more room than the files themselves).

    When ATI does a verification, it reads the file and generates new checksums and compares them to the old check sums -- one bit off means a byte off means a checksum failure means file fails validations. Once ATI reads a disk to create a backup, it never compares anything in the file to anything on the disk. This is part of the reason you can get false positives and false negatives when doing validations.

    You can get false positives or negatives, or both in many of the medical tests that you can receive these days -- that alone is not a reason not to be tested. ;-)

     
  13. Ur_Bob

    Ur_Bob Registered Member

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    I'm puzzled now.
    Based on the description of how validation of the archive works, I would expect the verification process to be much quicker than the original archiving process since it is only necessary to read the data.
    I have a Full backup, a Differential backup and an Incremental backup which is the first one done after the Differential.
    The Incremental backup took just under 4 minutes, the verify took about another 2 hours 30 minutes.o_O
    Can anyone explain the time?
    Backup is to a USB2 drive.
     
  14. Xpilot

    Xpilot Registered Member

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    Ur Bob,
    A probable explantion of why an incremental validation took so long is that in order to ensure that there is a complete image it is necessary for the process to check all the increments right back to and including the original base image. This applies even though all the parts were previously validated.
    The situation is even more long winded if you are using " Backup Locations" or a secure zone. In those cases all the images in those places will be re-validated even though they are not related to the current backup set.

    I avoid all this madness by not running validations at all. Instead I swap over hard drives and do actual restores. This gives 100% proof that all is well.
    Once confidence has built that one has a robust system these restores can be as infrequent as you are prepared to live with.

    Xpilot
     
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