Wonderings on the practicalities of RAID0

Discussion in 'MacBook Pro' started by johnnj, Apr 1, 2011.

  1. johnnj macrumors 6502a

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    Dec 11, 2008
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    #1
    Hi.

    I just switched from my ancient 3/2009 15", which since I got it, had to OCZ Vertex 1 128 gig drives in RAID0. With my new machine (see sig) I'm running those same ssds. I'm planning on upgrading them to a pair of undecided 256 gig drives, for space not performance increase.

    So, I'm looking at the results of a Xbench disk test and I see a max write of 337 MB/s and 286 MB/s read. If I halve that and convert to gbit/s it's 1.31 for write and 1.11 on the read. Far below the max of the SATA2 bandwidth of each controller, right?

    What I'm wondering is even if the SSD is SATA3 and the controller is SATA3, is the non-testbench most perfect performance that the manufactures spec the drive at is the controller speed even relevant? Even if I get a new pair of drives that are 2x the performance of the current ones in the same configuration, it's still under 3gbit/s for each controller. Are people finding that they're saturating the SATA3 controller on the optical drive interface?

    The other thing I'm wondering about is how a RAID0 volume on these machines reacts to one member drive being SATA3 and the other SATA2. I suspect it won't make a difference because it's only software RAID. In my years of experience with actual RAID in the real world everything's always been on dedicated controllers in machines somewhat larger than a laptop.

    So, I know that there's a new generation of SSDs about to hit the virtual store shelves but that there seems to be ones already out there like the Crucial C300 series (which will probably get cheaper soon) that are better than what I have now (and bigger, I want a pair of 256) but not better than what'll soon be available. Is it worth waiting for faster drives which might not show any demonstrable improvement over the current high end ones?

    I would appreciate any thoughts and insights that you folk might have on these questions.

    John
     
  2. systole macrumors member

    systole

    Joined:
    Mar 24, 2011
    Location:
    Minnesnowta
    #2
    I would suspect that utilizing a software raid solution would negate any performance gains of SATA-3, instead treating the SATA-3 drive as a SATA-2 equivalent. While I haven't tested this on SATA 3, That was my experience combining SATA and SATA-2 under ubuntu's software raid. Good luck on the other Q's
     
  3. johnnj thread starter macrumors 6502a

    Joined:
    Dec 11, 2008
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    #3
    OK, that makes sense. I think it'll probably behave exactly as you saw under Ubuntu. Thanks.

    John
     

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