Mac Pro Upgraded - 3xSSD's in RAID0

Discussion in 'Mac Pro' started by VirtualRain, Dec 29, 2009.

  1. VirtualRain thread starter macrumors 603

    VirtualRain

    Joined:
    Aug 1, 2008
    Location:
    Vancouver, BC
    #26
    I've had zero issues with my G1's (knock on wood). It sounds like you may have just been unlucky with yours as it would appear to have been a hardware failure. Other's here are having file system issues with the G2 drives in RAID with 10.6.2. So far, it seems the G1's in RAID0 on 10.6.2 are fine. At least my prior array of two drives and this stripe of 3 seem to perform flawlessly.

    At any rate, living on the bleeding edge does require a good backup strategy in the event the worst should happen.
     
  2. playalistic macrumors regular

    Joined:
    Sep 27, 2007
    Location:
    Surrey, UK
    #27
    Slightly OT I guess, I've just installed 2 x 80GB X25-M G2's in RAID0 but have yet to decide on the block (or properly known as stripe) size. I'm thinking 64k but wondered if the cell size of the Intel drives needs to be considered regarding write amplification etc etc.
     
  3. robains macrumors regular

    robains

    Joined:
    Nov 27, 2009
    Location:
    California
    #28
    The best answer is you will need to experiment. There are so many variables (including firmware versions, cache size, controller, etc.) - a good testing program will show you how well the drive works over varying file sizes, a really good testing program will show you how well the SSD works at close to maximum capacity.

    There are several testing tools, such as QuickBench (has not been updated for SL), BlackMagic Disk Speed Test, and others. Or just create your own tests with the files you most commonly use.

    Rob
     
  4. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #29
    Given the way the data is stored on Intel's SSD's, 128K is best in this regard IIRC.
     
  5. playalistic macrumors regular

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    #30
    Argh, I chose 64k in the end. Wondering whether I should blow the volume away and start again? Hmm.
     
  6. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #31
    That's up to you. There's no long term data as to how a smaller stripe would affect the drive's reliability that I've seen.

    But the 128K size should offer an increase in throughput.
     
  7. playalistic macrumors regular

    Joined:
    Sep 27, 2007
    Location:
    Surrey, UK
    #32
    Cool. Well I think I'll leave it for a bit then in that case. There certainly is no shortage of speed /throughput right now :)

    One more noob question. Am I right in thinking I can slap in another 80GB at some point and rebuild the array to include it, with no loss of data and without having to reinstall? Or am I on crack?
     
  8. nanofrog macrumors G4

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    May 6, 2008
    #33
    You can get it into a stripe set with the existing drive, but I'm assuming you're using software RAID (logic board + OS X).

    So you won't be able to do what's called Online Expansion (can add drives to increase capacity while retaining data). Instead, you'll have to make a backup of any files you need first, then make a set of the two drives. The initialization step will wipe any existing data, and why you must backup first (even with a proper hardware controller, it's still a good idea anyway, just in case). Install the OS, and restore any files from backup.
     
  9. playalistic macrumors regular

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    Surrey, UK
    #34
    OK thought as much. Cheers. I have a time capsule to save my ass if anything fails so no problems there :)
     
  10. VirtualRain thread starter macrumors 603

    VirtualRain

    Joined:
    Aug 1, 2008
    Location:
    Vancouver, BC
    #35
    The 64K stripe should work just fine for reading.

    Where a large stripe size benefits SSD's is on writing, particularly when the drive becomes used up and you start getting hit by the write-erase block penalty.

    As everyone knows by now, a whole block needs to be read and rewritten if any portion of it is used. I recall anecdotal information that Intel uses a 128K block size, implying that a stripe of 128K would be ideal, but some tech sites seemed to suggest that most SSD blocks are 512K in which case, the largest stripe option available would be the best.

    At any rate, you may as well run your array with 64K stripe size for a few months or more until you feel the need to rebuild the array, at which time you can do a secure-erase and restart with a 128K stripe size.
     
  11. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #36
    I was thinking of writes, as that's when wear/damage occurs to the drive. Hence the 128K suggestion.

    Hopefully, playalistic would test the write throughputs as well, but I should have clarified. :eek:
     

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