Which to use - incremental or differential backup

Discussion in 'Acronis True Image Product Line' started by fdm2000, Jun 12, 2008.

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  1. fdm2000

    fdm2000 Registered Member

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    I am a newbie and have successfully created a full image backup of my internal HDD onto a Seagate external HDD using TI 11 Home and am somewhat uncertain regarding the advantages/disadvantages of incremental versus differential backups.

    Would some experienced users provide their thoughts and advice on which type backup best suits the needs of one who simply wants to keep the external HDD in sync with the internal. I am a home user and do not create many data files, so backups for me are just to capture new programs/utilities or updates to OS, programs or drivers.

    Thanks,

    Frank
     
  2. Allen L.

    Allen L. Registered Member

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    Hi,

    Differential backups contain *all* the changes made from the last full backup in *each* one you make + all the original files, so they can be very large in size. The advantage of them is that the last one made will restore all your changed files to that time.

    Incremental backups are made using only the files that changed from the original first incremental backup you make (which will be the full size of the partition). So the first one could be 5GB and the next 2MB as the 2MB one contains *only* the changed files from the original 5GB one. You would have 2 incremental files totaling 5.2GB.

    Only thing is, you need all the incremental backups you made in order to restore and bring the partition back to the original size and complete with all updates to the present...loose one incremental 'chunk' and you are 'up the creek'.

    With the differential backups, you can use the last one made and have all the files updated without needing the previously made files, but each one made is a bit larger than the last made as it contains the changed files + the originals. You *could* also delete each older file as you make the new one and be OK, where as you need *all* the incremental parts you made to restore, say 1 through 6 or whatever.

    Hope this is clear enough.

    Remember, for space saving and very quick backups, use incremental. You may end up with several files, but each backup can be made quickly and will only contain the changed files since the last incremental one.

    :)
     
    Last edited: Jun 13, 2008
  3. fdm2000

    fdm2000 Registered Member

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    Many thanks for the explanation - since I have a 250 GB external FreeAgent Seagate HDD, I tend to favor the differential as you explained it rather than deal with multiple incrementals.

    Could you elaborate on your comment: "You *could* also delete each older file as you make the new one and be OK" relative to the differential backup. How exactly does one do this?

    Is there a correct or preferred method for deleting the original (previous) full image file? Does one simply select it and hit delete or is some other method used? Also can this be done after creating the differential backup?

    Possibly elementary dumb questions, but at age 76 the learning curve is steep.

    Thanks again Allen,

    Frank
     
  4. Allen L.

    Allen L. Registered Member

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    With differential backups you only need the latest one to be current - so you could delete the previous .tib files. With incremental backups you need them *all* to restore, as each one is just a part of the others.
     
  5. JustAnotherNoob

    JustAnotherNoob Registered Member

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    I'm glad that you were successful at that (I read your previous two threads where you posted your initial problem). Would it be possible to update the original thread(s) on how you solved the problem making the full image ? Maybe other people on this board can benefit from what you've learned.

    Yes, you can remove these files by clicking (Shift+) Delete in Windows Explorer, just like for any other type of file. However, make sure you never delete an original full image file until you have a made a more recent full image. Any combination of differential or incremental images is completely useless without the full image they were based on !!

    I don't think there is a one-size-fits-all answer to this question, as it depends on the amount of data being imaged, how much space you have for storing images, the frequency at which you expect to image and/or restore, etc. Both types of back-up scheme will require making a new full image from time to time. Stringing dozens of differential images onto a full image is not efficient, as at some time the individual differential images will become almost as big as the original full image. On the other hand, stringing dozens of incremental images onto a full image may be more efficient, but carries much more risk, as it requires only one corrupt increment to invalidate all consecutive images.

    To explore a possible scheme, consider the following hypothetical example. Say you got a new PC for Christmas, with 20.0 GB of OS / program files. Suppose you make a full image in week 1 of January, followed by differential or incremental images each following week. Finally, suppose you install only a few programs in weeks 2 and 4 (0.2 GB each), but a huge Windows Service Pack in week 3 (3.0 GB). A typical size of the full image made in week 1 of January would be ~10.0 GB. Working with differential images would then result in image sizes ~ 10.0 GB (+ 0.1 GB) (+ 1.6 GB) + 1.7 GB ,
    while working with incremental images would result in image sizes ~ 10.0 GB + 0.1 GB + 1.5 GB + 0.1 GB
    In order to have an up-to-date image at the end of January, only the files in brackets can optionally be deleted. Note that in neither case, you can delete the 10.0 GB full image, at least not until you make a new full image, say in week 1 of February (that full image would be ~ 11.7 GB).

    That's about the way I do things: I make a full image at the beginning of each month, supplemented with an incremental image (1) each week (2) before and/or after each major software change. Personnally, I have a big external HDD reserved to keep many months worths of these images, but if you "simply want to keep disks in sync", you could delete all the January files once you have made the full image in February, or you could be a bit more on the safe side and wait until March or April to do this. Also, if your system doesn't change much over time, you could suffice with making a full image each trimester and a differential or incremental each month. But I think you catch my drift - ultimately, everyone has to find the scheme they are most comfortable with ...

    Happy imaging !

    JustAnotherNoob
     
  6. fdm2000

    fdm2000 Registered Member

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    JustAnotherNoob wrote:

    "I'm glad that you were successful at that (I read your previous two threads where you posted your initial problem). Would it be possible to update the original thread(s) on how you solved the problem making the full image ? Maybe other people on this board can benefit from what you've learned."

    Be happy to share my experience. Before starting TI11 I did the following:
    1. Ran CCCleaner. Adaware, chkdsk,defrag and an Optimizer.
    2.Shut down Windows PX firewall
    3.Disconnected from the internet
    4.Disconnected my other external HDD
    5.Shutdown my antivirus program and other open programs
    6. Disable all Start UP programs except Acronis

    Not sure which ones of the above resolved my failure to create a full image backup, but will run this checklist in all future backups.

    Frank
     
  7. JustAnotherNoob

    JustAnotherNoob Registered Member

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    Thank you for letting us know. If that procedure works for you, I guess that 's all that really matters. But personally, I would find that checklist too much of a hassle to go through each time. While I usually close most open programs on the taskbar before creating or updating an image, I don't do any of the other things you mention. Of course, our installed software will differ ; also, I use TI 10. I would be inclined to think that your problem is most likely situated in (5) or (6), as these may contain an application that is competing for your local hard disk with Acronis True Image, causing the instability you experienced. Of course, if you feel more comfortable doing the entire checklist, there's no harm in doing so.

    JustAnotherNoob
     
  8. fdm2000

    fdm2000 Registered Member

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    Thanks for you assistance and insights, JustAnotherNoob. Slowly I am getting my arms around T 11. Yes I agree that taking the 6 steps prior to creating an image is undoubtedly overkill, but for me it is preferable to the frustration of a failed operation.

    Since I don't create many new data files or programs, I think I will go with a monthly differential and a full image backup every trimester.

    If I have this sequence correct in my mind: I will have a full image (1st month) + 1 differential (2nd month) + full image 3rd month then delete earlier full image + differential.

    Does this procedural outline make sense?

    Thanks again,

    Frank
     
  9. tuttle

    tuttle Registered Member

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    That's not correct. An incremental backup contains changes since the latest backup on which it is based. For example, this scenario:

    Full backup + Incremental1 + Incremental2 + Incremental3 + Incremental4 + Incremental5.

    Incremental5 is the changes since Incremental4. Incremental4 is the changes since Incremental3, and so on. The advantage is that each Incremental will be a smaller filesize than a Differential or Full backup. Under my example, to restore your latest backup, which is Incremental5, you would need all six files: Full backup, Incremental1, Incremental2, Incremental3, Incremental4, and Incremental5.
     
  10. JustAnotherNoob

    JustAnotherNoob Registered Member

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    You're most welcome, Frank.

    As another poster mentioned in the original thread, by far the easiest way to circumvent whatever the problem you had, may be to create and update images with the TrueImage Rescue CD, especially since you'll only be doing it once a month or so.

    It certainly makes sense. To dot the i's and cross the t's: a trimesterly scheme would imply a full image (1st month) + 2 differential (2nd & 3rd months), then a new full image the 4th month etc. But that doesn't really matter: my main advice was to make a new full image from time to time, whether that's every two, three or four months, is a matter of taste - there is no exact science to it.

    More importantly: you don't have to delete the previous set of images once you have made a new full image. In fact, as long as the older set(s) of images doesn't take up disk space you need otherwise, I would advise to keep the latest 2 or 3 sets of images, as additional insurance should one of your images be corrupt at the time you need them. As with data back-ups, redundancy can be a good thing ! The only thing you have to do, is adequately naming your image files. As an example: the first full image I made this month, is called "DiskName_2008-06a.tib", to which I added some incrementals. After installing XP SP 3, I made a new full image called "DiskName_2008-06b.tib", to which I will be adding some incrementals later in the month. Somewhere in July, I will make "DiskName_2008-07a.tib", etc. Even though I could delete it, I will be keeping "DiskName_2008-06a.tib" for a while: (a) as a fall-back for the unlikely event "DiskName_2008-06b.tib" would be corrupt or otherwise unusable ; (b) to allow me go back to the situation prior to installing SP 3, if I would need/want to do so.

    Of course, disk images can take up quite a lot of space, so deleting old images is usually in order. But there is some merit in keeping a few (sets of) images at your disposal, rather than immediately deleting them.

    mmm... that was a longer reply than I intended to write - I hope the details don't cause more confusion than insight ...

    JustAnotherNoob
     
  11. Allen L.

    Allen L. Registered Member

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    You are correct tuttle, as I use the task scheduler to make my first incremental backup. If you use it, like I use it, the first backup it will make will be the full image -- that is if no other files of the same title you made in the task Scheduler are in that folder you use for the scheduler. The second incremental will have the tag xxxx.xxxxxx2.tib, the first make *my* way will have only the title xxxx.xxxxxx.tib .

    You're way of first making a full backup of the partition would be the 'clearest' way for most to understand.
     
  12. tuttle

    tuttle Registered Member

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    My point was not to propose a separate process. I wanted to correct what you said:
    This is not correct.
    No matter how the original image was created, the point is that an incremental is based on the latest image, not on the first image as you indicated. That's why all incrementals "in the chain" must be preserved. I want users to understand how incrementals work, so they don't do something disastrous such as delete interim incrementals. :)
     
  13. Allen L.

    Allen L. Registered Member

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    OK - to be 'technical'...my statement "Incremental backups are made using only the files that changed from the original first incremental backup" is incorrect, it should have said "Incremental backups are made using only the files that changed from the original backup". It should be known that all the incrementals and the 'Original full backup' are needed to restore, and also make, if one reads anything about "Incremental Backups" and the difference between them and differential backups.

    What a lot of people do on this forum, is not mess with either one of these methods as they use more than one file. These users make a full new image each time, as it will be newer and have less chance of errors that using any of the other backup image methods.

    I frankly use incrementals just to save time. If I do have the time, I make a new full image of the complete disk (all partitions).

    With version 6 until starting with version 9, you had to do this to retain the MBR if you were not imaging the full disk. From v.9 on, you could image only the active partition and retain the MBR and boot files.

    Whatever works for you - but according to most all of the longest members using Acronis True Image - they will use the full method backup and usually make it by using the boot disk. *That* is the safest, and probably the best, method to use, as too many issues can arise with other image methods.

    :)
     
  14. tuttle

    tuttle Registered Member

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    Sorry, but you are still getting it wrong. It's important to be clear, because many users come to these forums seeking help. You revised your statement to now say:
    Again, that is not correct. An incremental is based on a chain of images and most recently on the latest image, which itself is based on a previous image, not on the first image or original backup as you indicated. An incremental increments from the last image, and that last image is itself incremental from the previous image, and so on. That's why it's called "incremental".
     
    Last edited: Jun 17, 2008
  15. Allen L.

    Allen L. Registered Member

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    A incremental backup uses *all* the images made that are in the folder of that series to perform the backup. If as you say, "An incremental is based on the latest image" - then the only changes would be updating the files from *that* image. All images used in a incremental backup series need to be present to perform another incremental image in that series. What if there is a file in the first original image, or 'the complete 'whole' part' of the incremental series, that has never changed before, but changes now? Do you think the last incremental tib file say, number 6, will contain that file? It will not. You need all the incrementals together to create another correctly.

    What you are describing is a differential method of imaging in your last statement.
     
  16. tuttle

    tuttle Registered Member

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    Yes! You finally got it! :)
    Yes, I was too brief in my last message. My earlier explanation had more detail. Incremental5 is based on Incremental4, which is based on Incremental3, etc. The entire chain must be preserved in order to explore or restore the latest incremental.

    The point that I wanted to correct was that you kept writing that the incremental is based on the first or original image, which in fact is not sufficient. An incremental is based most immediately on the last incremental, but that incremental is itself based on an earlier incremental, all the way back to the original. Each incremental is based on the previous incremental, and the chain begins with a full image.

    Full backup + Incremental1 + Incremental2 + Incremental3 + Incremental4 + Incremental5.

    Incremental5 is the changes since Incremental4. Incremental4 is the changes since Incremental3, and so on. The advantage is that each Incremental will be a smaller filesize than a Differential or Full backup. Under my example, to restore your latest backup, which is Incremental5, you would need all six files: Full backup, Incremental1, Incremental2, Incremental3, Incremental4, and Incremental5.
     
  17. Allen L.

    Allen L. Registered Member

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    OK! :;) But the only thing is, we have now completely confused the original topic starter, fdm2000! :D

    As I stated earlier for fdm2000 - the safest and surest method will be to create a complete whole image of the hard disk - and that is especially true if you are inexperienced with this 'imaging' stuff. If you are a bit more adventurous, create a partition image...but create either from the boot disk (out of Windows), and forget all the incremental and differential backups.

    Most 'newbies' have only one partition, so just image it completely each time. Mess up the operating system - no problem. No hassle with where in the hell did tib file #5 go from my incrementals? Hard drive go down, no problem either - just one file to grab...your full backup tib.

    :thumb:
     
  18. tuttle

    tuttle Registered Member

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    Most laptops nowadays have more than one partition, since there is usually a smaller partition used for system restores. I think even many desktops have a restore partition, because the manufacturers don't want to ship system CDs.

    In that case the user should image the entire drive and not just an individual partition.
     
  19. fdm2000

    fdm2000 Registered Member

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    Allen L and tuttle your interesting dialog was most enlightening and valuable for a newbie climbing the learning curve. I now have a much clearer understanding of the TI backup alternatives and options and how each fits into the overall scheme of things.

    Thanks for your involvement,

    Frank
     
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