special situation with incremental images

Discussion in 'Acronis True Image Product Line' started by eclipse3337, Mar 18, 2005.

Thread Status:
Not open for further replies.
  1. eclipse3337

    eclipse3337 Registered Member

    Joined:
    Mar 18, 2005
    Posts:
    8
    Hello,

    I have a question about a special situation regarding incremental backups.

    Suppose that:

    - I have made a FULL backup of my Win XP system partition (Day 0)
    - After that I made one incremental backup of the same partition every day (scheduled or manual)
    - Say, that I have been doing this for 4 days, so now I have the full backup and 4 incrementals, each from different days.
    - At this point I realize that something is wrong with my system and I decide to restore it to an earlier state.
    - Now I have 5 choices: the base and the 4 incrementals, which together represent the state of my Win XP config at 5 different points in time (from Day 0 - Day 4). Right?
    - I find that I have to return to Day 2 so I do a "Restore Image" and select day 2 in the list of times that I can go back to.
    - All is fine and I continue my work.
    - On Day 5 I want to make the usual daily incremental backup. Since I have made a task for it, it would still be based on the original image (I don't type in any file names, just run the task)

    How does True Image handles this situation?

    ------------------------------------------
    Day 0: Full backup, base image
    Day 1: incremental
    Day 2: incremental
    Day 3: incremental
    Day 4: incremental
    Day 4: ** PROBLEM ** -->> restore to Day 2
    Day 5: incremental
    -------------------------------------------

    On Day 5 when I want to make the new incremental image, the system states that images from Day 3 and Day 4 represent are invalid (regarding the current state of the system they never happened), which means that Day 5 incr. image should be chained back to the image from Day 2, not Day 4. Right?
    What happens to the images from Day 3 and Day 4?
    Are the deleted automatically when the new incr. image is made?
    Are they kept, should I decide later that I still want to return to Day 3 or 4?
    If they are kept, is the information that the image preceeding Day 5 is the image from Day 2 maintained? (I think it should be to ensure file system consistency)

    Thanks for reading this far.

    Eclipse3337
     
  2. Acronis Support

    Acronis Support Acronis Support Staff

    Joined:
    Apr 28, 2004
    Posts:
    25,885
    Hello Eclipse3337,

    Thank you for your interest in Acronis True Image (http://www.acronis.com/homecomputing/products/trueimage/).

    When you create the 5th incremental image it will be created to the 4th one (providing the 4th one is still available). It will take into account the difference between the current system state and the state that was when you created the 4th one. Briefly, Acronis True Image will always create the new incremental to the last existing one.

    Thank you.
    --
    Ilya Toytman
     
  3. eclipse3337

    eclipse3337 Registered Member

    Joined:
    Mar 18, 2005
    Posts:
    8
    Thank You for the quick answer Ilya.

    But I think, we have a problem.

    The result of the 5th incremental in this case (and all successive ones) WILL most probably BE AN INCONSISTENT FILE SYSTEM that does not match the state of the system at the time the 5th image was taken. I think it should be obvious why.

    Therefore I think it should be strongly emphasized in the user's manual that after making a restore, all incremental images made after the time the system was restored to, should be deleted before making a new incremental or else you will get garbage as a result.
    I have just looked through the manual again and have not found anything about situations like this.

    While we are at it, a few other questions:
    How does TI know what sectors have changed since the last backup?
    Does it make the comparison just before taking the inremental or is there some kind of a tracking mechanism activated after making an image?



    Regards.
     
  4. Acronis Support

    Acronis Support Acronis Support Staff

    Joined:
    Apr 28, 2004
    Posts:
    25,885
    Hello eclipse3337,

    Please note that Acronis True Image doesn't trace the changes until you actually start the image creation. When you start to create the incremental image the snapshot of the disk is made (the same as when you create the full image) and then Acronis True Image creates checksums of current disk clusters and compares them to those of the previous image.

    In the case described above the 5th incremental image will include the changes between the state of the system when the 4th image was created and current state. Even if you change something on the hard disk without booting into Windows (with some special utility for example) these changes will be included into the image as well.

    Thank you.
    --
    Ilya Toytman
     
  5. eclipse3337

    eclipse3337 Registered Member

    Joined:
    Mar 18, 2005
    Posts:
    8
    Thank You again for the quick answer.

    It is actually good news in my opinion,that TI does not rely on any kind of realtime tracking to make incr. images, for this way we can make incrementals when booting from the Acronis boot CD, not just from within Windows. Right?

    What You wrote about the other thing is really just another way of saying that I am right:
    But, in my case the current system was never in that state reflected in the 4th image, because it was restored to the 2nd image and then it went "forward" on a different path (hopefully, otherwise it wold have arrived to the same problem that made the restore necessary :D ).
    This means that without deleting the incr. images taken between the current time and the one the system was restored to (the 2nd), the comparison is made between the current state and a never-existed state (the 4th).
    What will be the result of that? Certainly not the same as the difference between the current state and the one the system is really "coming" from (2nd incremental).
    This could lead to unusable backups that should never be used to restore a partition, which is really what one should expect in this case and if one really thinks it over is not that complicated to figure it out, but nevertheless I think it should be mentioned in the manual as a potetial problem source.

    Thanks.
     
  6. Acronis Support

    Acronis Support Acronis Support Staff

    Joined:
    Apr 28, 2004
    Posts:
    25,885
    Hello eclipse3337,

    The system was in the state coresponding to the incremental image 4. Only in this case you were able to create this image in fact. It doesn't matter in what way you have changed the system after that. Even if you than format your hard disk, install clean Windows and then create the 5th incremental you will be able to restore your system from any image you have The whole set of images (one full and subsequent incrementals) may be considered as one image that has several restore points.

    Please note that the way the system was changed doesn't matter when you create the incremental image. The two things that are taken into account are: current state of the system and the state saved in the previous (full or incremental) image.

    Thank you.
    --
    Ilya Toytman
     
Thread Status:
Not open for further replies.