4 Drive SSD RAID 0 Mac Pro 5,1

Discussion in 'Mac Pro' started by riggieri, Mar 7, 2016.

  1. riggieri macrumors newbie

    Joined:
    Apr 30, 2012
    #1
    Hey All

    I am building a MAC Pro 5,1 with a 4 Drive SSD Raid in the drive bays. I am only seeing speeds around 600 MB/s, when I am expecting 1-1.2GB/s. Is this a limitation of the internal SATA controller?
     
  2. leon771 macrumors regular

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    Sep 17, 2011
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    Australia
    #2
    You've hit the SATAII limit. Better off building raid that uses a pcie controller and. It the Apple backplane.

    Should use pcie flash instead of sata based 2.5" drives or blades if raw speed is what you want.
     
  3. riggieri thread starter macrumors newbie

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    Apr 30, 2012
    #3
    SATA II LIMIT IS 3gb per channel and this is over four channels. I guess the apple backplane and controller are hitting about maximum on this anyways.
     
  4. h9826790 macrumors 604

    h9826790

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    #4
    1) Your SSD may have only 150MB/s, some smaller (e.g. 250G SATA SSD) only has this write speed. Therefore, 4x150=600

    2) For some better SATA SSD, may hit the 250MB/s read/write speed bottleneck due to SATA 2 limitation. So, the best you can achieve is about 1000MB/s, no way to achieve 1.2GB/s

    For high speed storage, simply get a PCIe SSD is a better way, 4 SSD in RAID 0 means 4x the failure rate, and the best you can achieve is just about 50% of a single PCIe SSD can do. So why take the risk but not go for simpler setup which have better performance?
     
  5. leon771 macrumors regular

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    #5
    T
    The backplane board SATA2 limit is 660MB/s from memory.
     
  6. Squuiid macrumors 6502a

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    Oct 31, 2006
    #6
    255MB/s on a Samsung 850 Pro 512GB here. Definitely not more on SATA2.
    But yes, that's one channel.
     
  7. h9826790 macrumors 604

    h9826790

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    #7
    S
    So, all 6 ports share that 660MB/s? I have absolutely no idea about this, may I know any reference for that. Nothing offensive, just want to know the truth.
     
  8. Machines, Mar 8, 2016
    Last edited: Mar 8, 2016

    Machines macrumors 6502

    Machines

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    #8
    cMP have an aggregate SATA backplane upper throughput limit of about 650 MB/s , across the four drive connectors . It's host computer chipset related , not drive related per se . That's why it doesn't make much performance difference between using SSD and HDD in this situation .

    Solution is to grab a mini SAS PCIe card and internally mount the SSDs in your Mac Pro . OWC has a Newer Technology card .

    http://eshop.macsales.com/item/NewerTech/MXPRMS6G1E1I/

    maxpower_minisas_1e1i.jpg
     
  9. Squuiid macrumors 6502a

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    Oct 31, 2006
    #9
    Yep, and use a MaxConnect to connect the drives using the existing SATA power in the backplane.
    http://www.maxupgrades.com/istore/index.cfm?fuseaction=category.display&category_ID=351
     
  10. h9826790 macrumors 604

    h9826790

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  11. Squuiid macrumors 6502a

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    #11
    No, I don't think so.
     
  12. Machines macrumors 6502

    Machines

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    #12
  13. Squuiid macrumors 6502a

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    #13
    Depends if the OP needs a 12Gbps or 6Gbps fan out cable ;)
    Your link is for a 6Gbps cable.
    And yes, their website is HORRIBLE.
     
  14. Machines macrumors 6502

    Machines

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    #14
    Depends if the OP needs a 12Gbps or 6Gbps fan out cable ;)
    Your link is for a 6Gbps cable.
    And yes, their website is HORRIBLE.

    The OWC Newer Technology RAID card I linked is 6 Gb/s , so that would be the limiting factor .

    And the OP's SSDs are likely non-enterprise grade 6 Gb/s SATA .

    Areca does have a 12 Gb/s mini SAS RAID card ( ARC-1883LP ) compatible with OS X 10.11 El Capitan , with an internal connector :

    http://www.areca.com.tw/products/1883.htm

    Things do get more expensive with everything at 12 Gb/s , of course .

    The throughput he desires (around 1100 MB/s) can be achieved with three x 6 Gb/s SSD in the array , Since the OWC Newer Technology card is not bootable in OS X , that would leave one SATA backplane available for a separate drive with an OS X install .
     
  15. throAU macrumors 601

    throAU

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    #15
    Possibly not enough PCIe lanes allocated to the on-board SATA controller(s) to run all channels flat out at the same time.

    The classic mac pro was designed in a time where SSD was rare and super expensive, it wasn't really expected to deal with devices that can saturate the SATA bus to the extent that SSDs can. When the older Mac Pro came out allocating 1:1 bandwidth in terms of PCIe -> max SATA channel speed would have been a waste.

    Can maybe get around this with a PCIe card.
     
  16. Machines macrumors 6502

    Machines

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    #16
    I just happened to think that for very high end bandwidth requirements , installing a mini SAS RAID card would require PCIe Slot 2 installation in a Nehalem cMP . A lot of these cards require 8 lanes electrical and at PCIe Rev 2 specs this would provide 8 x 500 MB/s ( = 4 GB/s) performance , minus any overhead .
     
  17. sauria macrumors regular

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    Texas, USA
    #17
    Isn't there an unused SATA port in this Mac Pro.
     
  18. lowendlinux Contributor

    lowendlinux

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    #18
    No..

    that was 3,1 and older
     
  19. sauria macrumors regular

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    #19
    Thanks.
     

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