Defragging

Discussion in 'General Returnil discussions' started by CloneRanger, May 11, 2011.

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  1. CloneRanger

    CloneRanger Registered Member

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    @ Coldmoon

    Hi, i realise this pertains to other similar Apps as well, so i'm NOT picking on you ;)

    I don't understand why/how defragging can affect the Real data whilst V-Apps are enabled. If the Real data etc is untouched when in session, & all changes dropped when not, how can/does DF make any difference or alter anything ?

    Either data on the Real system is sacrosanct or it isn't !

    TIA
     
  2. Coldmoon

    Coldmoon Returnil Moderator

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    Hi,
    Don't confuse what is happening when you defragemnt a disk. The system and OS make no difference as the key is defragmenting the actual disk itself. As the tech in RVS/RSS works at the disk level, defragmentation can cause damage through a type of control conflict; so while our tech is watching the disk for changes, the file system changes are not being monitored at the same time...

    Mike
     
  3. CloneRanger

    CloneRanger Registered Member

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    @ Coldmoon

    But the system and OS are on the disk ?

    But i would have thought that the file system changes "should" be dropped on unloading the V-App, hence no changes ?

    Re - control conflict

    Is this something that can be addressed in a satisfactory manner, or just one of those things ?

    Go easy on me, i'm a bit thick :D But genuinely wish to know/learn :thumb:
     
  4. Coldmoon

    Coldmoon Returnil Moderator

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    Think of it this way:

    Rearranging where a file is located on the disk does not inherently change that file or its contents. IOWS, the file does not change so no changes are tracked, but the physical location of that file is now different than where the OS thinks it should be so is either missing or, in the worst case scenario, is moved to a portion of the disk where it might be partially or fully overwritten causing the file to be damaged.

    To prevent this type of thing from happening, Windows must be updated with the proper file locations on the physical disk which cannot happen if you are virtualized.

    As the old saying goes, an ounce of prevention is worth more than a pound of cure...

    Mike
     
  5. CloneRanger

    CloneRanger Registered Member

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    @ Coldmoon

    Sure, but if NO real changes are made to the disk whilst in V-mode© those file locations etc etc can't have Actually moved/changed, as they are only Virtually happening, so NO actual damage etc can occur. I would have thought/expected !

    To me, if ANY V-App, not just Returnil, is NOT supposed to alter the Real disk whatsoever whilst in V-mode© then Nothing should change, leaving aside intentionally saved stuff to a created Special folder/s. Or is it ONLY this/these SF's what would be damaged, are you saying ?
     
  6. Coldmoon

    Coldmoon Returnil Moderator

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    You have to understand the underlying tech in both Returnil and a defragmentation solution. Both are designed to control the disk at a low level to be able to do what they do. The defragmenter moves files on the real disk to rearrange the physical locations of files and parts of files for better performance.

    So let's say you have a file with some MD5 hash on your hard drive and it is fragmented so that pieces of it are all over your HDD. Further, let's assume that no changes have been made to this file prior to the defragmentation operation. Simply putting that file back together by defragmenting it will not change the MD5 hash of the file, only where the parts of that file are located; even if the parts of the file are now stored within contiguous sectors of the disk (The parts are all next to each other in sectors of the disk that are all next to each other).

    IOWs, all that happened was that you taped that office document together after your daughter took the desk scissors to it and threw the pieces around your office and put it back in your file cabinet where it was supposed to be. In this example, your daughter did not write on the document with crayons or pen, but simply played the "cut up daddy's paper" game. So you acted like the defragmenting solution and the OS as well by not only putting the document back together, but also filing it where you can get to it again later when required.

    This is somewhat similar to what is happening with the Virtual Mode and defragmentation as the drivers for the defrag solution will still be able to move the files around the disk (that pesky control conflict I mentioned previously) while RVS/RSS will take the OS back to a time before the defragmentation.

    This scenario does not mean that damage would occur automatically, but it heightens the chance that it will. We found this happening during the early RVS 2007 series and was a major reason for simply blocking the defragmentation operation until the Virtual Mode was inactive.

    Mike
     
  7. CloneRanger

    CloneRanger Registered Member

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    Understood

    Yes, but in V-mode© it hasn't Actually Really happened = NO permament real changes are "supposed" to occur !

    But it shouldn't be able to !

    So it "can" occur, even though it's not supposed to ! It does seem very strange because, either V-mode© means Total V-mode© or it doesn't, and it should.

    Thanks for your patient & helpful attitude & answers to my probing :) I guess more work needs to be done with Any/All V-mode© Apps that don't Totally protect the Real disk in V-mode© ;)
     
  8. cm1971

    cm1971 Registered Member

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    I was confused about this too. I would defrag before starting virtual mode and reboot and defrag again and it would show fragmentation.
     
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