RAIDing SSDs for boot?

Discussion in 'Mac Pro' started by JesterJJZ, Dec 13, 2011.

  1. JesterJJZ macrumors 68020

    JesterJJZ

    Joined:
    Jul 21, 2004
    #1
    I currently have a pair of 80GB Intel SDDs in RAID0 for boot in my MP1.1. A couple years ago cost was played a part in this decision. From what I remember there was also a slight speed advantage. Is that still the case today? Considering a new MP (once released) and going through my options. Since, the optical drive takes up one of the extra SATA ports, it would leave me a port short from my current setup. Is one larger SSD better than two in RAID for boot today?
     
  2. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #2
    RAID 0 improves sequential performance, but not random access in the real world, which is what booting relies on (striping can actually slow random access down :eek:). But it made sense cost wise at the time, as I recall a pair of 80GB's were cheaper than a 160GB. Always a compromise... ;) :p

    So a newer SSD would improve matters so long as it's random access performance exceeds what you currently have. :)
     
  3. JesterJJZ thread starter macrumors 68020

    JesterJJZ

    Joined:
    Jul 21, 2004
    #3
    So you're saying one SSD is better than two no? :D
     
  4. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #4
    It will depend on the drives being compared.

    For example, lets say your 80GB Intel's can generate 70MB/s for random access performance (likely the single disk performance, as random access is not doubled as sequential access is in real world testing), and a newer SSD you might be looking at, even though it's a SATA III model, only generates 50MB/s, then your existing disks would be faster.

    So the best thing to do IMO, is take a look at independent reviews of the drive's you're interested in, and compare them to what you already have for random access throughputs.

    Now there are RAID levels that do improve random access performance, but that means 10 if you plan to use Disk Utility, or a proper hardware RAID controller, in which RAID 5 would not only become an alternative, but is actually faster than 10 for both sequential and random access throughputs (why relational databases have shifted from 10 to 5 in the last 5 years or so).

    Unfortunately, if you decided to go with a RAID 5 implementation, and do a lot of writes to that volume, then you'd want to use SLC based SSD's due to the higher write cycles that result from the parity writes (won't really be an issue if your usage is predominately reads = less expensive MLC based drives would be acceptable in that case).
     
  5. JesterJJZ thread starter macrumors 68020

    JesterJJZ

    Joined:
    Jul 21, 2004
    #5
    Yeah, I'm only looking at one large vs 2 smaller SSDs for boot. Probably Intel. I have those now, two in my MP 1.1 and One in my MBP. The MBP is pretty zippy with one SSD, then again it's a newer machine. I'm leaning towards wanting a single SSD for my next tower.
     
  6. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #6
    I don't blame you.

    If cost isn't an issue, then it's nice to keep one of the SATA ports available for another drive to fill the ever increasing need for storage capacity. :D

    Unfortunately, though SSD prices are getting better, it's still the most expensive in terms of cost/GB.
     
  7. Loa macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #7
    Hello Nano,

    What about IOPS? Is that important for boot volumes? If I recall the Intel G2s had very high IOPS, even compared to some of the current drives.

    Loa
     
  8. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #8
    Random access performance is a better indicator of boot performance IMO.
     
  9. Loa macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #9
    Thanks!

    Loa
     

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