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COMPRESSING Drives

Discussion in 'Storage' started by WOOKZ, Oct 19, 2009.

  1. WOOKZ

    WOOKZ New Member

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    does compression of the OS drive hamper proformance
     
  2. mosheen

    mosheen

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    i'll say YES
     
  3. i789 New Member

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    since you have to decompressing your OS when you use it, so I say you will take performance hit but depends on how much you compress it, the difference is going from small to a lot.
     
  4. newtekie1

    newtekie1 Semi-Retired Folder

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    Definitely, not only does every file have to be decompressed before use, but the decompression and compression on every file access adds system overhead. The compression is smart enough to not compress the most commonly used OS files, but it still gives a pretty big hit on performance.
     
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  5. [Ion]

    [Ion] WCG Team Assistant

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    Yep, I had it set on my laptop because of the small disk (60GB), but it made things far slower, so now I just keep all of my junk on the 500GB disk in my desktop.
     
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  6. RejZoR

    RejZoR

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    The hit is not all that high, even on lower end laptops. But it's there. Besides, with Windows Vista and above, you won't be able to compress system files when UAC is enabled. So, you'll be able to only compress data files.
     
  7. DanTheBanjoman Señor Moderator

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    Pretty big hit? Happen to have some numbers on that?

    From what I know there are even some cases where NTFS compression improves performance, can't find a decent article atm though. I haven't run any benchmarks on compressed drives in ages, though one of the drives in my server is compressed and I don't notice any performance issues (perhaps it's a few % lower, but certainly not a "pretty big hit"). I'm guessing performance increases basically can happen when compression is high enough to reduce disk access enough to matter (ie 50% compression > 50% less reading from disk) and CPU's being able to decompress faster than it would take the disk to read that other 50%. Though I can't back that up with any actual facts.
     
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  8. DanTheBanjoman Señor Moderator

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    [​IMG]
    It's the legacy disk, thus no RAID applies (for those who think it's some array). The controller doesn't have on board cache either that affects anything.

    [​IMG]

    [​IMG]
    A bit hard to read due to the cached read, but the write speeds seem fine, even though you can't read it very precise.
     
  9. Mussels

    Mussels Moderprator Staff Member

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    when you use file compression, in order to read them they have to get uncompressed into system memory, and written temporarily back on the HDD.


    its not an optimal solution at all.


    XP/vista/etc already compress some files, mostly system restore/SP uninstall folders and such.
     
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  10. W1zzard

    W1zzard Administrator Staff Member

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    there is a break even point, when the drive takes longer to read the data than the cpu needs to compress/decompress it and you have that amount of cpu power idle anyway
     
  11. DanTheBanjoman Señor Moderator

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    Why? Source?
     
  12. Mussels

    Mussels Moderprator Staff Member

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    i remember it from a course i took, which made me go and format my HDD's to a 64K cluster size... which then made XP impossible to install due to service pack 2 cracking the shits about not being able to compress its uninstaller.

    its half related, but its WHY i remember it.


    will google for details now


    ding, found it


    http://support.microsoft.com/kb/307987

    underline my emphasis



    more
    http://support.microsoft.com/kb/251186/EN-US/
    it may be me interpreting it wrong, but it clearly sounds like its decompressing it to a file and not leaving it in memory
     
  13. W1zzard

    W1zzard Administrator Staff Member

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    it [ntfs compression] decompresses to memory

    it's not even half related .. it's 0 related .. well it uses the same word, but that's it
     
  14. DanTheBanjoman Señor Moderator

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    The installer doesn't work on file system level though.
     
  15. DanTheBanjoman Señor Moderator

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    And I doubt it will decompress the whole file first, I'm guessing it decompresses the stream of data on the fly, similar to network compression. I can try with some large iso, gimme a min.
     
  16. Mussels

    Mussels Moderprator Staff Member

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    i'd install XP, it'd go well, then it'd BSOD on boot.

    ok w1zz, so its 0.00001% related - like i said, its just WHY i remembered it.
     
  17. W1zzard

    W1zzard Administrator Staff Member

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  18. Mussels

    Mussels Moderprator Staff Member

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    weee, a PDF!


    its not like i'm going to disagree with evidence here, i was merely stating what i had been taught (and until now, beleived due to lack of contrary evidence)


    edit: i read that, and dont see it mentioned specifically whether or not decompressed files are left in ram, or decompressed to the drive.


    edit 2: thinking about it, what i learned may have been the compression used on fat32 drives (if there was one?) it was around the early XP days when i did this course.
     
    Last edited: Oct 27, 2009
  19. DanTheBanjoman Señor Moderator

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    FAT32 doesn't have compression, you're probably speaking of things like drivespace/doublespace/norton speeddisk/etc. Those do not work on file system level.


    I just formatted a 128MB USB stick as NTFS and enabled compression. I wrote a 56MB file to it twice. So ther eis no space to decompress anything. When I double click either file it instantly opens, so it's not decompressing the whole file, just the stream of data. Also, it's not storing any of this to the stick. You could argue it's storing elsewhere, I doubt that. Test that yourself by using a single drive for the OS and filling it completely. I'm pretty sure the system won't crash because it can't read files.
     
  20. Mussels

    Mussels Moderprator Staff Member

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    good test dan, ah well.
    my guess would be that if it WAS storing it somewhere, it would be on the C:\ drive in a temp folder - perhaps test with a large file, open it, and then see if your free space lowers?

    i need to get proven wrong on something at least once a month, or my ego gets too big :p
     
  21. DanTheBanjoman Señor Moderator

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    It's file system level compression, why would it use Windows directories? I doubt the file system actually asks Windows where to store files.

    I think it's best to compare to playing porn on your computer. You select the middle of the movie (the part where they lez it out), the system reads only that part of the movie and decompresses those frames on the fly. It does not decompress the whole movie on the disk before it can play anything, it does not require temporary files of any kind. It's instant access to compressed data without fancy requirements. And sure there probably is some small buffer in the memory, but I doubt it's large enough for you to notice it.
     
  22. Mussels

    Mussels Moderprator Staff Member

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    hahhaha, porn references. awesome.


    (i'm not arguing with you on this, merely getting as much information as i can)
     

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