How many OWC SSDs can you put in RAID0?

Discussion in 'Mac Pro' started by psychometry, Sep 8, 2010.

  1. psychometry macrumors regular

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    Oct 5, 2006
    #1
    Does anyone know how many OWC SSDs you can put in a RAID0 before you reach bandwidth saturation?

    What would be the maximum number of drives if you use a hardware RAID controller on the 16x PCIe slot? I assume you could use more drives than connecting on the Mac Pro's SATA backplane but I'm not sure what the exact number would be in practice.
     
  2. WardC macrumors 68030

    WardC

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    #2
    This is a great question. If anybody can answer this, let me know, I'd like to know this myself. I think that for best performance, you can do 4xSSD in the 4 main drive bays with a 16x PCIe SATA card.

    The ultimate solution, however would be the OCZ Z-Drive R2 P-88 2TB PCIe SATA RAID solution. It's a PCIe full-length card with 8 channels populates with SSD flash drives that fits in your PCIe slot and runs a simultaneous 8 times 256GB RAID memory system giving you s total of a 2TB RAID drive at 16x PCIe speed. But the retail price on this is $9685.99. Mac OS X support is coming soon.

    Here is the link for more info:

    http://www.ocztechnology.com/products/solid-state-drives/pci-express/z-drive-r2/slc-enterprise-series/ocz-z-drive-r2-e88-pci-express-ssd.html

    You can buy one from Amazon here:

    http://www.amazon.com/OCZ-Technology-Drive-Express-OCZSSDPX-ZD2P882T/dp/B003EEMIHW/ref=sr_1_7?s=electronics&ie=UTF8&qid=1283984117&sr=1-7
     
  3. ZennZero macrumors member

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    #3
    Nanofrog has some good posts on this subject. See here and here, for instance.

    And here is some data from Barefeats backing that up.
     
  4. Transporteur macrumors 68030

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    #4
    All his posts are good, the ones you linked do however not target the OP's question.

    Considering that the PCIe x16 link is good for 8GB/s (which would require a 32 port controller that can handle the full SATA 3GB/s speed on each port), the maximum amount of SSDs you can put into a RAID0 before throughput saturation completely depends on the controller you use.

    Personally, I haven't seen a 32 port controller, 24 and 16 seem to be more common, especially with those that are compatible with OS X.

    From a physical point of view, mounting 16+ SSDs in the Mac Pro is no big deal. There's more than enough space
     
  5. ZennZero macrumors member

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    #5
    They answered the first part of the question. He *then* asked about a PCIe raid controller, and as you said, performance is a function of the controller itself in that case.

    Also of note from the Barefeats article (and I don't know if this is still the case in the 2010 MPs):

    "Apple has introduced a new Pro RAID card that's trick. It does not require a mini-SAS cable connection to the motherboard like last year's RAID card. It signals the motherboard of its presence in slot 4 and takes over the control of the internal drives.

    That's "green" as Ruby Rhod would say in Fifth Element, but, according to Apple's own info, it's limited to 550MB/s -- even slower than the internal SATA controller. Arghh. There are third party SATA/SAS host adapters with the Intel IOP348 and internal mini-SAS ports that go up to 1200MB/s, but they CAN'T be used in the Nehalem Mac Pro -- at least until Apple shares the secret to their cable-free trick."
     
  6. Transporteur macrumors 68030

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    #6
    It still applies for the 2010 models as they are basically exactly the same as the '09 models apart from a new firmware that supports the new hex cores and faster clocked RAM.

    The Apple RAID card shouldn't be used, it is completely overpriced for what it delivers.
    You're better with third party RAID cards such like ATTO, Areca or even Highpoint, which offer better performance and expandability.
     
  7. psychometry thread starter macrumors regular

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    Oct 5, 2006
    #7
    At the moment, I have a 3Gb/s Areca RAID controller. Now, according to Google conversion, 3Gb/s = 0.375GB/s = 384 MB/s. So if the OWC SSDs max out at 285MB/s wouldn't you only need two to max out the throughput of my controller?
     
  8. beaker7 macrumors 6502a

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    Mar 16, 2009
    #8
    That is 3Gb/s per channel. How many channels is it?
     
  9. Transporteur macrumors 68030

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    #9
    The 3Gb/s apply for the SATA port, not the controller. Each SATA port on your controller (SATA 3Gb/s, also known as SATAII) has a maximum theoretical throughput of 384MB/s, as you said. In a real life application, the SATA 3Gb/s channel levels off at about 270 to 280MB/s, so the OWC SSD saturates the port completely.

    Your controller (depending on which model you've got) has a much higher throughput than that. Some models can easily reach 1GB/s or even more.

    A little more information about your exact controller would be much helpful to say how many SSDs you can hook up to it before you run into bandwidth limitations.
     
  10. psychometry thread starter macrumors regular

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    Oct 5, 2006
    #10
    It's this one. Looking at some of the details, it does appear that it's 3Gb/s per drive port. I missed that distinction.

    So, would I actually be limited by the PCIe 16x bus, rather than the RAID controller, or is there some other hard limit to the controller that's not listed anywhere?
     
  11. Transporteur macrumors 68030

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    #11
    Your controller is PCIe 8x, but still you wouldn't run into the limitations of the PCIe slot with that controller since it has only 4 ports, so a theoretical maximum throughput of about 1GB/s.
    Keep in mind that a single PCIe channel makes 500MB/s, so the 8x port is good for 4GB/s.

    What might limit the bandwidth of the controller is its processor. I'm not sure if the IOP348 the 1212 would result in any limitations, but I'm pretty sure nanofrog can give a clear statement on how many SSDs to use with this specific controller.
     
  12. Transporteur macrumors 68030

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    #13
  13. VirtualRain macrumors 603

    VirtualRain

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    #14
    The limit on the ICH is around 660 MB/s. I'm hitting that limit now with 3xX25-M in RAID0... http://forums.macrumors.com/showthread.php?t=841556

    I think 2 modern drives on the ICH is the best solution that gives you max performance without throttling.

    Cheap low end RAID cards are even worse with some I/O processors having max throughputs of around 500MB/s. (eg. my old Areca 1220)

    A high-end RAID card would be essential to support the 1GB/s kind of throughput necessary to support 4 drives in RAID0.
     
  14. alphaod macrumors Core

    alphaod

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    #15
    I just want to clear up that the Areca ARC-1212/1222 is actually only x4… It has a x8 length connector, but the card itself only supports up to 4 lanes channels. That's what Areca told me.
     
  15. Honumaui macrumors 6502a

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    Apr 18, 2008
    #16
    I have a 1222x its x8
    now the 1212 is 4x drives the 1222 is 8x drives ? was that the confusion on arecas side ? but both are x8 interface

    not doubting areca told you that :) but wonder if the guy at areca was reading the spec and read the number of drives it supports on the 1212 in confusion ?
     
  16. Ryan P macrumors regular

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  17. alphaod macrumors Core

    alphaod

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    #18
    No I needed my second slot on my Mac Pro for a second video card, so I called the Areca guys up and asked them if the card needed the x8 PCIe lanes; that's when I told the card actually only supports x4 PCIe lanes, so they can be put in any slot.

    (I noticed I said "channels" in my previous post—I meant lanes)
     
  18. Honumaui macrumors 6502a

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    Apr 18, 2008
    #19
    no worries on the channel lanes thing :) when I am perfect I will bitch :) I am far from perfect :) I knew what ya meant

    it can run on a x4 ? but its x8
    will be fun to get to the bottom of this though :) hehehehe
     
  19. VirtualRain macrumors 603

    VirtualRain

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    #20
    It may not matter how many lanes the 1222 can utilize... from a quick search I did, it appears the IOP348 on the 1222 can only handle about 550-600MB/s which is less than the Intel ICH10 (660MB/s). You will almost saturate that with 2 SSD's.

     
  20. Honumaui macrumors 6502a

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    Apr 18, 2008
    #21
    http://arecaraid.com/forum/viewtopic.php?f=7&t=18
    and
    http://arecaraid.com/forum/viewtopic.php?f=7&t=10

    did he have proper discs ? did he have the proper firmware at the time ?
    I dont buy it human error of some kind to get that low of number ?
     
  21. VirtualRain macrumors 603

    VirtualRain

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    #22
    That appears to be the result of cache on the 1222. If you look at the graphs of the throughput (second link), there are two sections of most graphs... one that's seeing 1200MB/s and the other that's averaging around 600-700MB/s... the former is reflective of the the cache performance, while the latter is the true I/O performance (after the cache has been depleated). The average of those two is what AJA reports in the top panel.

    The fact is that the 1222 max's out at somewhere well below 1GB/s... only the cache makes it look faster... and that's not something that should be dismissed... it is a tangible benefit. However, 2 SSD's will nearly saturate this card - 3 will for sure.
     
  22. Petered macrumors newbie

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    Aug 5, 2010
    #23
    If it's a standard

    If it is done the same as a windows machine it's 24 a guydoes It on you tube!!
     
  23. nanofrog macrumors G4

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    May 6, 2008
    #24
    You should be able to run 4x SSD's on it without throttling, so long as the SSD's aren't 6.0Gb/s models that can exceed what 3.0Gb/s ports can handle (3.0Gb/s tops out at 270 - 275MB/s, so 4x ports = 1080 - 1100MB/s).

    The processor should be able to handle that in a stripe set (800MHz processor, and stripe sets aren't that strenuous).

    ARC-1221 = SATA model (8 external ports, IOP341 series, and it's a discontinued model)
    ARC-1222X = SAS model (8x external ports, IOP348 series)

    They're definitely different cards (not using the same IOP processors), and the stripe sizes or other equipment used in the tests aren't listed either.
     
  24. Honumaui macrumors 6502a

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    Apr 18, 2008
    #25
    that second link was *Benchmark* ARC 1221x (SATA) vs ARC 1222x (SAS)
    so the 1222x was on their also :) just widen your browser maybe you will see it :)
    so the reason for the two links :) one shows with SATA drives and the second showed it with SAS drives :) the way the site is you have to make sure your browser is wider though to see it ;)
     

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