Guide To RAID

Discussion in 'Links' started by grunger, Sep 2, 2005.

  1. Mr. Spock

    Mr. Spock Member

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    I just set up a RAID 0 using two 74GB WD Raptors with a 16k stripe size.

    Since this is my first RAID 0, I have no other setup to compare to.

    I received information from this link.
     
  2. littledragon

    littledragon Member Guru

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    I redid the raid with a 4k block size and it definately feels faster. It literally takes 5 seconds from the time you see the xp screen to the desktop. I don't count the post time cuz that varies with the different bios's out there.
     
  3. grunger

    grunger Ancient Guru

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    The question of what block size to use for the stripe is a tough one.
    Basically the smaller the block size, the smaller the pieces a file is split into and therefor the more disks can be used at the same time to perform a write.
    A small block size with only 2 disks while it not likely to be as good, as with say 4 or 8 disks.
    A small block size may possibly increase write performance, however as the file is split into smaller chunks the locations of the small blocks will be more fragmented therefor leading to poorer read performance, its a balancing act.
    Basically the more disks you have the lower the block size should be
    The block size choice often depends on the type of application using the disks, e.g. a database will benifit from a smaller block size than a game load will.
     
    Last edited: May 5, 2006
  4. grunger

    grunger Ancient Guru

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    The only real difference between the 'raid edition' WD's is the higher MTBF (Mean Time Between Failure) rating meaning the disks are more reliable than standard disks - 3million operational hours on the raid editions i think
     

  5. littledragon

    littledragon Member Guru

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    the way I see it is with a bigger block size, say 64k is that files smaller than 64k will be stored on a single drive, essentially taking performance down if it's only reading off one drive for that file. i believe the files smaller than 64k are evenly distributed across the drives but still gives poor performance. I have yet to bench the new setup, I probably should since it's a new windows install.
     
  6. grunger

    grunger Ancient Guru

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    Yes, it is the size of the blocks to be written, so a 63k file will be written to one disk only if the stripe size is 64.
    It depends as i said on the type of apps running: a 8192kb file and a 2k stripe size = 4096 writes locations over 2 disks, and would lead to poor performance reading back as it is so scattered, whereas a 4k file and a 2k stripe = 2 writes, so reading back will be as if it was just reading 2k from a single disk = better performance.
    To get the best performance you need to work out the average file size moved on your system frequently
    Benchmarks only use smallish files and therefore the bench performance always gives better results with smaller block sizes, however this is not real world performance
     
  7. Saiyanora

    Saiyanora Active Member

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    Just looking at your link they are comparing a 7200 rpm drive against RAIDed 10k drives... a stupid, irrelevent test.
     
  8. Mr. Spock

    Mr. Spock Member

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    I should have gave the link from the begininning of the article.

    The author had built a total new system and used his older 2 yr old system as a bench/comparison for the improvements gained. This was not a test comparing hard drives or the like.
    The point was (upon reading further), that a 64k stripe was used and while it had good performance, it was found that a 16k stripe provided even better performance. As evidenced by the picture below the comparison. (where the suther states "Update").

    Sorry for the confusion.
     
  9. Soldaten

    Soldaten Master Guru

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    Although i'm running a clucnker of a rig right now...(A64, 512 PC2100, 6600 pcci-e, and a single ATA66 120 gig drive, alomg with a usb external drive, damn i mis my rig back home. I miss my rig back home.) right now when I had a coupla of SATA 150's in raid 0 i did some experimenting. Formatted as NTFS volumes/partitions/etc, do better with larger patitions and block sizes. Even up to 128 I had some improved performance.
    Then I threw in an older ATA133 with a block of 32 and the where quite similar. The only difference was that the FAT32 disk was only 6.? gbs. The Raid array wa over 250gbs with partitions as large as 40+ gigs.
    I'm not alone in the because a lot of colleages stick with FAT32 on on any disk/partition smaller than 8 gigs with a block of 16 or 32 (sometimes even 8).
    Just remember how much space you waiste with a 128K block. Any file as small as 10K will still occupy the entire block.
    Personally I recomemend 64 if you're packin dual 250 gig SATA II drives, because lets face it, it would be quite hard to fill the entire drive.....especially for a gamer like myself.

    Currently in Iraq everybody and I gotta that you all for your PC and Tweaking ?'s because it can take my mind from the hell aaround me....even if only a minute or two. But iths enauiogh. Thanks again PC nerds, lol
     
    Last edited: Jul 1, 2006
  10. thecake90

    thecake90 Ancient Guru

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    Here is a pic to explain RAID enjoy
    [​IMG]
     

  11. grunger

    grunger Ancient Guru

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    Now thats funny :) :) :)
     
  12. Jonny5isalivetm

    Jonny5isalivetm Master Guru

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    lol Very funny :D

    okay so considering RAID 0....

    Will Windows load any quicker say with a pair of 10K Raptors rather than a Single...

    What exactly would be the best strip size?

    thanks folks




    J5
     
  13. guardz

    guardz Master Guru

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    Hey if Im adding another HD to my system (I only have the one atm) to RAID 0 them, would I need a fresh install of windows!?? Its not like fully installing a whole new single HD is it?
     
  14. grunger

    grunger Ancient Guru

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    You would need (Idealy) an exact match for your current HDD, then you would need to create the array - meaning the total destruction of any data on the drive
     
  15. guardz

    guardz Master Guru

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    ..meaning a whole fresh sysetm install! ? SIGH. :(
     

  16. Jonny5isalivetm

    Jonny5isalivetm Master Guru

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    nobody wanna reply to me ??????????? :(

    Currently Using HD in My Sig and windows Gets Past the Loading Bar Screen in around 3-4 Secs
     
  17. grunger

    grunger Ancient Guru

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    It might be slightly quicker but 3-4 secs is pretty fast already i wouldn't bother spending money trying to get that quicker.
    RAID 0 is (is i've said before) only worth it if your into heavy video encoding or Database running, it might make the load times on a game a bit quicker, but this is not worth the money or the risks associated with running RAID0.
    The only RAID configs i ever really use are RAID1 or RAID5, both have the built in redundancy.
    My server runs SCSI RAID5, although sata raid 5 controllers are available they are around £150-200+the cost of 3xMatched disks.
    If you really want to run raid0, then fine, the best stripe size i have already discussed previously, but between 64kb and 128kb are normally best but it depends on useage (and bear in mind the stripe size which makes a bench run quick may not the same stripe size which makes real-world usage quick)
     
  18. bumblebee13

    bumblebee13 Member

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    This is beginning to confuse me, what's the difference between strip size and cluster size or are they the same thing?

    And if they aren't, what would be the best sizes for each for a Raid 0 set-up which is being mainly used for gaming, no heavy encoding etc (i'll be using 2 x 160GB hitachi deskstars 7,200rpm).
     
  19. grunger

    grunger Ancient Guru

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    Please read the whole thread
    The stripe size is the min size a file must be to be split accross the disks, eg if the stripe is 64kb and a file is 62kb it will be written only to 1 disk - no RAID advantage
     
  20. bumblebee13

    bumblebee13 Member

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    I have, but it seems opinion differs greatly with people reccomending from 4kb to 64kb. I'm thinking of going for 4kb, 8kb or 16kb... probably 16kb, but i'm not sure yet and was wondering what the best was for my purposes
     

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