RAIDing all 4 drive bays

Discussion in 'Mac Pro' started by ifraaank, Aug 3, 2016.

  1. ifraaank macrumors regular


    Jun 25, 2012
    Odense C, Denmark
    Hello guys.

    I'm thinking of buying 4x 250GB ssd's to put in my Mac Pro. I currently have nothing in the drive bays. Would it be possible to RAID 0 all 4 bays? And since it's SATA 2 ports (250mb/s each) would that give me a speed of about 1gb/s? And 1TB of space? Or are there some limits with controllers or something?

    Thanks :D
  2. jbarley macrumors 68040


    Jul 1, 2006
    Vancouver Island
    I'll work just fine but, make sure you have a very good backup plan and stick to it religiously.
    If you do try it, please post us some benchmark results.
  3. Draeconis macrumors 6502a

    May 6, 2008
    It'd be limited to the top speed of the SATA controller, which I believe is less than 1Gb/s. I tried something similar to this once, by zeroing out 4 drives in these bays. I hit something close to 1Gb/s, but then the controller I think wasn't happy and the speed dropped dramatically.

    You'd be much better off getting an AHCI SM951 and a Lycom DT-120. PCIe 2.0 will limit you, but you'll still get 1.5Gbps read/write, for far less than 4x SATA SSDs. You'll also still have those 4 bays free for other things.
  4. buster84 macrumors 6502

    Oct 7, 2013
    This would be a better option to get full speed. Then you can keep your 3.5in bays open for the big drives.

    4 drive 2.5 thunderbolt enclosure
  5. chrfr macrumors 604

    Jul 11, 2009
    The old Mac Pros with multiple drive bays don't support Thunderbolt.
  6. thats all folks macrumors 6502a

    thats all folks

    Dec 20, 2013
    Austin (supposedly in Texas)
    what are you hoping to achieve? what do you want this to do?

    you wont get the maximum performance x 4 with a simple software RAID, especially using Disk utility. If you want to use those bays, have a look at SoftRAID. It will give you more options and better results.
    as Draeconis mentioned, a PCIe based controller is a great option for getting around the SATA II limit. I like this one,

    and if you want to put SSDs in the Mac Pro bays, you need new sleds,
  7. Analog Kid macrumors 601

    Analog Kid

    Mar 4, 2003
    I'm using this in an early 2008 to good effect:

    The $70 isn't much compared to the cost of the SSD's, and I could use the mSATA SSDs which give me a bit more flexibility if I ever want to reuse them.

    I did this a couple years ago so I don't remember my benchmarks, but I was pleasantly surprised by how close to the theoretical limits I was able to get.
  8. whwang macrumors regular

    Dec 18, 2009
    I think the true limit is about 500MB/s, for all internal bays together. The bottleneck is not the SATA, but somewhere else.

    I use all the five internal bays for RAID0 with 5 Hitachi 4TB drives. The RAID0 never exceed 500MB/s. Of course they are not SSD, but each of them is capable of about 200MB/s. So don't expect 1GB/s.
  9. PowerMike G5 macrumors 6502

    Oct 22, 2005
    New York, NY
    I'm running my 5,1 Mac Pro fully maxed out. I have 4 x 6TB WD Blacks occupying all 4 SATA slots in RAID 0. These are the fastest HDDs you can get on the market right now. I'm averaging around 560MB/s both read and write on a 24TB volume. I think that's the fastest you'll get on an internal RAID via SATA as the controller caps somewhere around 660MB/s for all the ports on the Mac Pro combined.

    I am also running a 3 M.2 PCIe SSD RAID 0 via the Amfeltec x16 PCIe card and averaging around 3500MB/s for that RAID. So you can get faster speeds via PCIe. But it all comes down to your needs.
  10. h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    I think 4 small size SATA SSD is much cheaper than 1 large PCIe SSD. isn't it? A 128G SATA can cost lower than $30, 4x128G just cost around $120. A single SM951 already cost >$200. And the cost difference will getting bigger and bigger when size increase.

    Anyway, I am quite sure the 4 SATA 2 bay are shared bandwidth, that means impossible to get 1000MB/s.
  11. Draeconis macrumors 6502a

    May 6, 2008
    I got a 128Gb SM951 and Lycom DT-120 for £83. Reads at 1.5Gbps (capped by PCIe 2.0), writes round 750Mbps, with impressive IOPS.

    Say you got 4x 120Gb Samsung 750 Evos. Best price I could find is on Amazon for £47. So £188. Plus, you'd need something to attach them to, as they don't attach to the sleds normally. You could just get a simple 2.5" to 3.5" adapter, such as a dock for a Raptor drive, they're normally around £9, so 4x is £36. £224. Or you could be cheap and use gaffa tape, who knows ;) But you're limited by the SATA controller to a max of around 660Mbps red/write, and could suffer disk failure of any one of 4 units, taking out your entire array if using RAID0.

    So, even saying you're cheap, and attach the 2.5" drives to the sleds with gaffa, you're still spending £188.

    2x 128Gb SM951s in RAID0 scale really well, and aren't capped by the SATA controller, so you'd get roughly 3Gbps read, 1.5Gbps write, decent IOPS, for £166.

    I guess it depends what you're after, more space or more speed?

    I wanted a fast OS and Apps, but don't need SSDs for media. 1 SM951 for the OS is fine, all my media is stored on 4x 2Tb 7,200rpm disks using with OpenZFS. Runs really well, configured in RAIDZ (basically RAID5) so can suffer one failure without any loss of data. I then replicate this to a FreeNAS box running RAIDZ2 (RAID6).
  12. ifraaank thread starter macrumors regular


    Jun 25, 2012
    Odense C, Denmark
    I already have the Lycom DT120 and a 512GB SM951 as my boot drive. But I was looking for a fast scratch disk with loads of space. I already have these 4 bays free, and wanted to use them for something :p Just not hard drives, they're noisy.

    Sadly, my Mac Pro doesn't support thunderbolt.. :(

    Thanks for the answers guys, I'll look into it! Might just go with two in RAID 0 then if that benefits me in any way.
  13. h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    No, OP was talking about plug that into the native port. There is no adaptor require. Just plug a SSD in, leave it at there is fine. I myself has SSD like that. No extra cost, the SSD is so light, and the SATA port is actually strong enough it hold the SSD at there for years. If worry, a tape can help for virtually zero cost.

    We only need SATA 2 speed SSD, so, no need to go for any expensive model. I got my 120G SSD for less than $30, a brand call DGM (link in my signature). Via a native SATA 2 port. I can't feel any different than my 1T 840 evo. Even running benchmark, they both capped at 250MB/s anyway.

    And you are comparing a total 480G SSD storage option to another 256G option with roughly the same cost. It's what I want to say, for the same size, SATA option should be cheaper. Unless go for the SATA 3 card. In this case, I will go for PCIe SSD (unless boot to Windows is required).

    However, I agree that the speed should max at about 660MB/s even RAID all 4 together, and ~4x failure rate.

    So, it really depends on if the user needs speed / size. However, if only need high IOPS, but not require high sequential speed. Nothing can beat the SATA 2 port option in term of setup cost.

    Also, occupy a SATA port is not necessary bad, if that helps to free up one PCIe slot. Of cost there are PCIe card can handle 4 PCIe SSD in full speed, but that's extremely expensive, so won't help to reduce cost.

    Anyway, my last post only want to point out that it's quite impossible to get a PCIe SSD storage option that can be cheaper than native SATA 2 port option (for the same size). I am not saying that PCIe SSD is bad, or not worth etc. If I have empty slot, I will also get a PCIe SSD, but at this moment, I even didn't install my SATA 3 card, because the 2nd GPU helps me more most of the time. And there is virtually no difference on boot time, loading time, etc by running the SSD via SATA 2 port and SATA 3 card. The random small files read write speed simply cannot saturate the SATA 2 bandwidth.

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