iMac SSD's in RAID-0

Discussion in 'iMac' started by ans167, Jan 24, 2011.

  1. ans167 macrumors newbie

    Joined:
    Jan 24, 2011
    #1
    I've got a late 2009 27" iMac and have been looking at some of the threads about replacing the hard drive with an ssd.

    I want to put in 2 ssd's in a RAID 0 set up, I found this enclosure which fits 2 2.5" ssd's into a 3.5" form:

    http://www.icydock.com/goods.php?id=121

    would this work in the imac? It is exactly the same size as a 3.5" drive, just wondering if anyone had tried this or knows anymore about it?

    Planning on putting some OWC Mercury Extreme Pro (not RE) drives in

    Thanks for any help!
     
  2. Hellhammer Moderator

    Hellhammer

    Staff Member

    Joined:
    Dec 10, 2008
    Location:
    Finland
    #2
    RAID 0 is useless with single SATA connection. One OWC SSD can already max out the bandwidth (~285MB/s) so you would receive no performance gain from two of them in RAID 0 unless you replace the ODD with one of them so both get their own SATA connection.
     
  3. ans167 thread starter macrumors newbie

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    Jan 24, 2011
    #3
    That enclosure puts them into a hardware raid-0 so surely there will be a bump in, at least, write speed? Large files would max out the bandwidth but not small ones. Two drives in hardware raid should be faster and more stable then a single ssd anyway.

    Anyone tested out the icydock dual raid convertor? It is marketed for Mac Pro's so would be great to hear if anyone has done some speed tests...
     
  4. Hellhammer Moderator

    Hellhammer

    Staff Member

    Joined:
    Dec 10, 2008
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    #4
    The enclosure isn't the bottleneck, it's the interface. There is only one SATA 3Gb/s connection in the enclosure, meaning that the maximum bandwidth is 3Gb/s or around 285MB/s in real world. That is what a single OWC SSD can provide. Sure, that 285MB/s is sustained speed, meaning that it will only work for "bigger" files (in benchmarks, 128KB is used for sustained so it can read a 128KB file at 285MB/s). Random speeds do not benefit from RAID 0 as they don't scale up like sustained speeds do.

    RAID 0 is twice as insecure as a single drive because if one drive fails, all data is lost. You would have more cons than pros because of RAID 0. If you're lucky, you may see <5% increase in performance over a single drive but IMO that is not worth it.

    If you really want RAID 0 SSDs, replace the HD with one and the SuperDrive with another one. That way both get their own SATA connection and you can take the full advantage of RAID 0. Otherwise I would just get one big SSD
     
  5. ans167 thread starter macrumors newbie

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    Jan 24, 2011
    #5
    Thanks for that, I think I understand now! I'm new to this RAID stuff..

    I will look into the performance boost I might get for my kind of work to see if the RAID would be worth it. I've seen some pretty impressive results on youtube etc..

    Thanks for your help :)
     
  6. wfriction macrumors newbie

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    Jan 24, 2011
    #6
    Might I ask why you would want to get 2?
    I would say just go with the biggest OWC (good choice btw) SSD you can afford.
     
  7. ans167 thread starter macrumors newbie

    Joined:
    Jan 24, 2011
    #7
    Well if you set up hard drives in a RAID-0 configuration they can read and write faster because the system thinks they are one drive but data is actually written to all drives simultaneously. In theory, 2 drives are twice as fast as 1 etc etc.. It also less tolerant to faults - if one drive fails you loose everything, so a good back up/mirroring system is needed as well.

    http://www.youtube.com/watch?v=96dWOEa4Djs - a bit over the top but pretty amazing speed! There are some good mac raid videos on there too..

    But as Hellhammer pointed out, this wouldn't work that well in the iMac as there is only one Sata connection, which limits the speed to/from the drives.
     

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