SSD software RAID 0 in a 2008 MP

Discussion in 'Mac Pro' started by NoManIsland, Feb 17, 2010.

  1. NoManIsland macrumors regular

    Feb 17, 2010
    Hello, I have read through the related posts in the forum, but I was hoping to receive final confirmation before purchasing.

    I have a 2008 Mac Pro, with all four drive bays filled, and I was looking at placing two Intel X25-Vs (40 GB) in software RAID 0 in the optical bay (no mount - just sitting in there), to be used as my boot drive. I was going to use the two free SATA connectors on the logic board to connect the drives.

    First, will this setup be bottlenecked anywhere, and/or would you recommend a different setup to achieve the same thing? I also am not quite sure what cables I would need as I am shockingly inexperienced at DIY.

    My usage pattern is primarily running Logic and ESX24 to run the Vienna Symphonic Library to play my (classical) compositions, with some audio mixing to bring in the vocal elements (I'm working on an opera right now, for which I will use MIDI and voice). I'm hoping to get a performance boost in Logic from installing the SSDs.

    Please let me know your thoughts on this setup - thanks!
  2. jetjaguar macrumors 68030


    Apr 6, 2009
    there is a thread on this already and i believe the problem is running 2 ssds in the optical bay .. you dont have enough sata ports .. u have one for the second optical drive .. i think if u plug the second one in the logic board then the performance of the 2 ssds will be cut in half ? i could be wrong:confused:
  3. NoManIsland thread starter macrumors regular

    Feb 17, 2010
    Sorry, I only realized the other thread would have been suitable for this topic after I posted - this is actually my first post on any forum anywhere :(

    I wouldn't be using the SATA connection for the second optical drive, I would be routing cables from the main board to the optical bay - this is what solutions like MaxConnect and Transintl's Pro Caddy do, I'm just not bothering with a mounting system since they are SSDs. The main board on the 2008 Mac Pro has two SATA connections on it not used for the drive bays, unlike the 2009, which has only one - that may be what you are thinking about :)

    Mainly I'd just like to get confirmation from one of the forum sages before I go out and buy the drives, and especially I'd like someone with experience tell me what cables I would need and any feedback from their own installation experiences.
  4. nanofrog macrumors G4

    May 6, 2008
    It can be done, but it would only work under OS X (the ODD_SATA ports on the '08 systems won't run Windows drives whether it's HDD, SSD, or ODD <Windows install disk will stall - the drive itself would work under OS X>).

    Just get 2x SATA cables (RT angle on one end) for data, and a Molex to SATA Y splitter for power.

    You could run into another issue though; throughput throttling in the ICH, as it's limited to ~660MB/s (design limitation of the ICH), if there's simultaneous access with other drives in the system (figure a stripe set of 2x Intels can produce ~500MB/s reads, so you've only ~160 MB/s remaining for any other drives). This is only a problem if access is simultaneous though. But it's to be expected, as I presume you're going to use the SSD stripe set as a OS/applications drive.
  5. NoManIsland thread starter macrumors regular

    Feb 17, 2010
    Hello Nanofrog, and thank you for your response :)

    Yes, I intend to use the SSD stripe for my OS and Apps drive. I don't think the Windows issues will be a factor as a VMWare Fusion installation of XP is more than sufficient for my occasional Windows apps - but thanks for the head's up.

    I'm not sure I understand the throttling issues, but it is precisely the kind of info I was looking for. Where I would be most concerned about this is that, although Logic will be on the SSD pair, my Vienna Symphonic Library takes over 260 GB, so it won't fit and will be on my 2 TB Caviar Black. I will definitely be using the two together at the same time, so do you think that this will cause an issue? If so, what would be the best solution?
  6. NoManIsland thread starter macrumors regular

    Feb 17, 2010
    Also, do you have any idea what length the different cables would need to be?
  7. nanofrog macrumors G4

    May 6, 2008
    2TB Caviar Black:
    Burst Throughput = ~249MB/s (read)
    Average Throughput (sustained) = ~119MB/s (read and write)

    X25-V (Intel's data, not from an independent review):
    Average = 170MB/s

    So 2x (170MB/s) + 119MB/s = 459MB/s (sustained or average throughputs) are what would be the norm, and the ICH is capable. :)

    It's possible you could hit it if both the SSD set and HDD are running in a high burst state, but it wouldn't last long.

    If you want to be sure however, you could get a SATA card (SIL3132 based) and attach the HDD to that (example). It won't boot OS X, but for a data drive, you won't need it to (Mac drivers are available from Silicon Image; here). Though there's 4x physical ports, it's only a 2 port card, and you can configure it to internal only, external only, or a 1 + 1 if you wish. Handy, as the other Mac compatible cards are eSATA only from what I've seen. The cost can't be beat either.

    Spec wise, it's SATA 3.0 Gb/s, so is fast enough for a mechanical drive, even the burst rate of the 2TB Caviar Black (theoretical limit of 375MB/s, but real world results are ~270MB/s - with any SATA 3.0Gb/s port).

    A cable length of 12" would be more than adequate IIRC (returned my '08 MP more than a year ago).
  8. NoManIsland thread starter macrumors regular

    Feb 17, 2010
    Would that equation still hold given that the two SSDs would be in RAID 0? Is that what you mean by 170 MB/s x2? I would have thought that the total bandwidth of a stripe would be more than the combined usual bandwidth, but I guess that makes sense. Also, just so I know, what does ICH stand for? Sorry if I am being ignorant :(
  9. nanofrog macrumors G4

    May 6, 2008
    Yes. In a stripe set, you get the single drive throughput * n members in the set. So in a 2 disk stripe, where the avg. throughput is 100MB/s, you'd get 200MB/s from the stripe set of identical drives.

    It's a bit more complicated when you're dealing with a mixed set (drives aren't the same models).

    ICH = I/O Controller Hub (aka Southbridge)
  10. NoManIsland thread starter macrumors regular

    Feb 17, 2010
    Thanks Nanofrog, that's exactly what I needed to know. I've read a lot of the threads, and you are always a very knowledgeable contributor, so a special thank you for all the info you have posted that has helped me in the past -while I was a lurker :).
  11. nanofrog macrumors G4

    May 6, 2008
    :cool: NP. Glad it helped. :)

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