Can someone explain incremental sizes?

Discussion in 'Acronis True Image Product Line' started by kevinkar, Jan 17, 2009.

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  1. kevinkar

    kevinkar Registered Member

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    Hi,

    Using True Image Home 11, build 8101 I am creating incremental backups as I install software on a new computer I have recently built. I understand full, differential, and incremental backups and how they work. The question is what's up with the huge file sizes for the incremental backups I am generating?

    I have made one full backup and 9 differential backups. In creation order they are sized the following for the *.tib archive along with the size of the data on disk as reported in the True Image GUI:

    1. 1,688,739 - 4,631,000
    2. 3,679,025 - 5,721,000
    3. 3,675,276 - 5,795,000
    4. 4,681,822 - 7,434,000
    5. 1,165,999 - 8,535,000
    6. __839,767 - 4,810,000
    7. 3,692,059 - 5,869,000
    8. __541,849 - 6,249,000
    9. 4,244,443 - 6,712,000
    10. __942,610 - 6,788,000
    I do not defragment between backups. I am just loading software and moving on. I have browser caches, swapfiles, and any temporary data on another partition. I also remove any temp or installation files before making a backup as that's data that does not need to be restored. I also empty the trash before backing up. All my backups are done using Bart PE and the True Image plug in.

    What I see are backup archives that are much larger than I expect and the reported size of the data going up, DOWN, and then up again (such as between 5 and 6). I also see incremental sizes that are much larger than the size differences between the data such as the between 7 and 8 where the data on disk change was 400MB and the archive difference is 500MB (reasonable) whereas between 8 and 9 the difference in data change is 500MB yet the archive change is a whopping 4.2GB (totally unreasonable)!

    These numbers are not what I expect to see as *incremental* and are more like FULL backups.

    I have double checked to see that they are all definitely incremental and not full backups.

    So am I missing something or what?

    I am confused especially because I made incremental #9 on the 6th, have done practically nothing to the machine, and just now made a quick incremental as a sanity check. As you can see, #10 came out as a 70K difference on disk yet the archive was almost a GIGABYTE of "incremental changes".

    This can not be right.

    Can anyone explain this to me?

    Thank you,

    Kevin
     
  2. lesterf1020

    lesterf1020 Registered Member

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    Acronis records the difference in sector changes on the disk not file changes. If one or more of your programs is creating lots of tempfiles or your swapfile is regularly changing shape or system restore gets busy or you have some file damage you can easily end up with large incrementals. In general Operating System partitions do a lot of system stuff that rearrange the sector map resulting in large incrementals. It takes some planning to minimize this. It is one reason why I have put my data on a separate partition which results in small data backups.
     
  3. kevinkar

    kevinkar Registered Member

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    You missed the part where my temp and swap data are on other partitions. I also should have mentioned that my data (software installs, personal documents, etc.) is all on a separate hard drive so the only thing I am backing up is the OS and software as it's installed. I also have hibernate and system restore turned off.

    I agree that there is system level stuff going on but there is essentially *no* difference between incremental #9 and #10 yet the incremental was almost 1GB. I admit to not being an expert in file systems by any means but there's no way turning off the machine on the 6th, making an incremental, turning it on last night and making a new incremental should have resulted in 1GB worth of changes.

    Mind you I merely turned it off on the 6th, made the incremental, and shut it down. Last night I booted to the CD and made an image immediately. There should have been no difference yet it created a huge incremental.

    Kevin
     
  4. lesterf1020

    lesterf1020 Registered Member

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    I do not understand what you are asking. It is clear that you have already decided on the answer to your question by insisting on the conclusion you have come to. I would recommend you email or use live chat to complain to acronis about the "totally unreasonable" file size or choose another backup program that gives more "reasonable" incremental file sizes. Only an Acronis engineer has a chance of providing you with what you seek.
     
  5. kevinkar

    kevinkar Registered Member

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    Then please refrain from replying if you don't understand the question. As the Acronis website says, Acronis engineers regularly read this forum and I am awaiting their reply to help.

    Thank you.
     
  6. Acronis Support

    Acronis Support Acronis Support Staff

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    Hello all,

    Thank you for using Acronis True Image

    kevinkar, I am unable to tell why some of your backup files have the unexpected size.

    I can explain. Acronis software uses the following algorithm to create an incremental backup file: Acronis True Image uses a sector-level technology. During a full backup file creation the program creates a "snapshot" of the entire partition and it "remembers" the state of the partition, i.e. what exact sectors were "filled" and the sectors that were empty.

    When you initiate an incremental backup, the program compares the current state of the sectors with its "snapshot" and "includes" the sectors that were changed into the incremental backup file.

    I don't know what have you done exactly when the archive change was 4.2GB, but it appears that your actions strongly influenced the entire system.

    Thank you.

    --

    Oleg Lee
     
  7. kevinkar

    kevinkar Registered Member

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    Oleg, Thank you for the reply. I agree with your explanation as to how incrementals are SUPPOSED TO work but apparently are not doing so in my case for some reason.

    All I can tell you is that I boot to the CD (a Bart PE with the True Image 11 plug in), start up TI, select backup, click forward to the screen where I select the back up to which I am adding an incremental, select validate archive, and then OK. The end result is an incremental that seems much larger than it should be.

    The ONLY thing I think that may affect this is how I select the archive to update. In the browse window you see the list of archives of which the first full one is there as well as the incremental archives with the same name as the full with a number appended showing which particular incremental it is.

    Let's say I am going to make incremental #11. When I select which archive I am appending, am I supposed to click on the original full archive or am I supposed to select the last incremental #10? Perhaps I have been clicking on, say, #4. Even though the incremental that is created is automatically called #11, is it determining the changes between #4 and #11, not between #10 and #11? Is that possible? Does this explain the wildly different and huge incremental sizes?

    I don't recall exactly how I have been clicking but are we supposed to select the previous incremental and not a previous one? Is this just incorrect clicking on my part?

    I suppose I can test this myself but it would be nice to hear from you what the proper process should be.

    Thanks,

    Kevin
     
  8. bgoodman4

    bgoodman4 Registered Member

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    It stands to reason if you are selecting any but the last incremental backup that you will get a larger backup than you might expect. Seems to me you would be adding all changes to the PC that occurred since the selected backup. This would be minimized (logically) if you selected the last one. That being said I have found when scheduling backups that I have to select the full backup or the schedule does not work. I have not noticed especially large incremental when the schedule runs but then I have not really been watching this closely (but I have noticed when the PC has been inactive the incremental takes much less time to complete). Probably the best bet to answer this question would be to run some tests. Sometimes what seems logical is not how things work in reality.
     
  9. kevinkar

    kevinkar Registered Member

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    I don't think there's any other way to fully answer this question.

    If the software works the way it's supposed to (only changes since the last incremental) then it should create relatively small archives.

    When you select the archive to RESTORE, it knows to restore them in order, full to last incremental. It stands to reason that, if you CREATE an incremental, the software ought to know to back up changes since the last one that was created.

    If my "theory" is correct that I have been clicking the wrong thing (arbitrarily selecting an incremental instead of specifically selecting the last one there) it should be evident by recreating the entire set of incremental archives again. That's not something that's done in minutes. Will probably take an hour or more as TI has never been the fastest program in the world!

    However, if what I am doing is not intuitive or can result in the wrong results, it should definitely be put on the list of items to modify or fix at next release (basing the new incremental on the last existing one automatically instead of the user clicking one).

    I'll see what happens later tonight.
     
  10. MudCrab

    MudCrab Imaging Specialist

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    It shouldn't matter which "split/part" of the backup set you select when you do an Incremental. TI knows the files go together and will add it to the end. You should get the same results whether you select the Full, first Incremental, last Incremental, or any Incremental inbetween, for example.
     
  11. bgoodman4

    bgoodman4 Registered Member

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    I was definitely not able to set up an automatic incremental backup task when I selected the last file created on the full backup. It only worked when I selected the first one. Any time I run an incremental manually I always select the last file from the previous backup. Again, a test should ans the question one way or the other.

    As to the irregular size of the incremental I was thinking if you have a number of programs such as anti virus and malware that auto update it seems conceivable that these may be doing larger updates from time to time (perhaps on the same day) and that might account for some of the difference. Just a thought.
     
  12. kevinkar

    kevinkar Registered Member

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    Yeah, I have thought about that too but have been very careful to remove temp files and check folder sizes before running a backup. In every case (I have the numbers written down but they are at home) the changes were what I consider to be minimal. Installing Photoshop, for example, only adds about 1GB of changes but the incremental after that load showed an increase of 3.6GB! Yikes!

    As MudCrab noted the incremental should not depend on which one was selected in the GUI (which was why I was clicking arbitrarily in the first place) and running an experiment should produce the same results.

    I didn't get a chance to experiment last night but hope to tonight.
     
  13. kevinkar

    kevinkar Registered Member

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    Last night I ran what might be considered a poorly thought out experiment but it appeared to "work" as far as I am concerned.

    I restored all of my archives starting with the initial full backup and then worked through each incremental. After restoring each one, I created a new archive from that freshly restored partition.

    What I found out was that there appears to be some truth to my opinion that you MUST select the LAST incremental when creating the next incremental archive.

    While I forgot to bring my numbers to work with me and can not quote them here, I can tell you that each new incremental created by selecting the previous incremental and not just clicking the first full archive or arbitrarily selecting any previous incremental created a new incremental archive that was reasonable - each successive incremental archive was in line with the actual amount of data that changed on the partition (the delta between actual data change on the partition was close to the delta between the previous incremental and the new one.)

    So, while my experiment was not completely scientific or totally controlled, it appears that it's best to be careful and select the last incremental archive when creating the next one so that the resulting archive is in line with the actual size of data change on the partition.

    Something to possibly tweak in further versions if you ask me!
     
  14. MudCrab

    MudCrab Imaging Specialist

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    Can you provide some more details on the procedures you used?

    After each restore, was the backup you created a Full or an Incremental? If it was an Incremental, on what Full image was it based?
     
  15. kevinkar

    kevinkar Registered Member

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    Mud,

    I booted to the rescue CD (A Bart PE with TI11 plug in) and clicked the Restore button. I selected the original Full archive and restored that.

    I stayed in the GUI and clicked Backup and created a new full archive (you have to create a new one with a new name otherwise the new incrementals won't use the right name).

    I stayed in the GUI and clicked Restore. I selected the original Full archive and, in the list of incremental archives, selected the #2 archive. It should restore the Full and then appends #2 to it.

    I stayed in the GUI and clicked Backup and created an incremental but selected the NEW Full archive on which to append.

    I stayed in the GUI and clicked Restore. I selected the original Full archive and, in the list of incremental archives, selected the #3 archive.

    I stayed in the GUI and clicked Backup and created an incremental but again selected the NEW incremental #2 and continued.

    Repeat over and over. Restore an original incremental from the original list and create a new incremental in the new list.

    Does that clear up the process?

    Only thing I did not do was to reboot after each operation.
     
  16. shieber

    shieber Registered Member

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    The swap file isn't inlcuded in an ATI backup, just a placeholder for it since it isn't necessary for booting windows. So the size of the swap file at the time of backup, evenif it's on the partition being backed up, and and how many sectors inthe swap file have changed since the last backup should be irrelevent to the size of an inc/diff file.

     
  17. kevinkar

    kevinkar Registered Member

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    Even so, I have put the swap file on a different hard drive forever (at least the last 14 years or so - whenever it was I bought a second hard drive) so it's never part of the equation.

    I also always place my important data on a separate hard drive from the OS and back that up separately. The OS partition includes all the software I run but that's generally all that's there.

    I also remove all the temp Windows install stuff that gets created when I run Windows Update.
     
  18. norrisg

    norrisg Registered Member

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    You still seem to be missing the point that it is sector changes which matter. You can have exactly the same amount of used space in every directory as you had last time you did a backup and even exactly the same file contents, but still have a large number of changed sectors.

    Installing a product doesn't just change the sectors in which it ends up residing, it also changes sectors used for work files (work files are not just placed in the user temp directory), the MFT, the registry, etc..

    Any kind of background optimization or indexing process may be causing sectors to change too. Whatever your problem is, it seems highly likely it is something to do with your system, not with TrueImage in general as it would be a frequent complaint. An unusually large cluster size might cause far more sectors to be changed than normal too.

    BTW, do you see the same effect if you use differential backups?
     
  19. kevinkar

    kevinkar Registered Member

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    Oh no, I understand that point just fine. What's not making sense is that, such as in my last incremental, the result was an 11GB incremental file when the last full archive was also 11GB.

    There is no way that installing 200MB of data resulted in every sector changing again such that another full 11GB of "changes" were recorded. Even doing a basic calculation assuming only new sectors were written to in installing the 200MB of software does not equal 11GB worth of sectors to have incrementally backed up. Note that the software installed was not software that writes to Windows OS folders. All are mostly self-contained products that write into their own folders and very little into the registry.

    I also have posted before that I created an incremental image of a particular size and merely rebooted again into the same rescue environment and created another incremental archive that resulted in a large amount of "incremental changes". Theoretically, since I never booted into the OS, the second incremental should have been either 0 or very small (if True Image is really a true image - it should recognize there were no changes at all from the last incremental.

    In my opinion, there's no reason to perform incremental backups if the resulting data is as large (or slightly smaller) than a full archive would have been. That renders the incremental feature useless and more dangerous since you have to depend on a string of files to restore.

    No, I have not also tried differential backups.
     
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