Improving (multi-) I/O performance in Mac Pro

Discussion in 'Mac Pro' started by ceres, Oct 29, 2008.

  1. ceres macrumors regular

    Nov 14, 2007
    Dark Forests of Germania
    I am sort of shocked how much low I/O performance mars overall responsiveness of my mp. Whenever I have some disk intensive app running the entire system begins to stall awfully up to the point when a simple task such as browsing becomes a painfully slow process. This situation is even aggravated when I concurrently access a flash drive. I have 4 Samsung 1 TB F1s and 8 GB RAM available.
    Would building a software raid 5 help to improve the situation? I reckon that transfer rates are part of a problem.
    Intel´s latest SSD Drives are also much faster than my F1s and also sport much better access times. Has anyone experimented with using such a drive as the system and application drive?
  2. phrehdd macrumors 68040


    Oct 25, 2008
    I have to first respond to your question on software raid 5. Mac Pro doesn't have software based raid 5. You might be able to use a 3rd party software but if its there I would not trust it.

    There are a few things you can do to help your situation. The level of improvement would only be known after you tried these things.

    Some ideas

    Internal Raid to your Mac Pro.
    Options (too many but here are some)
    1) Stripe 2 of your drives to be used for large files but don't go beyond 75 percent full.
    2) Stripe 3 drives, keep 1 drive for just the OS.
    3) Stripe all of your drives into one volume. Just remember that EFI updates
    cannot be done on raided drives.
    4) Speed and safety - mirror drives (2 drives per a mirror) then stripe them. This gives you similar speed to a 2 drive stripe raid but if a drive fails, you still can continue working. Catch is that this gives you a 2 terabyte of space to work with instead of your 4. (again EFI updates wont work on raid drives so an external disk with OSX would have to be booted to do the EFI upgrade then you can go back to your internal drives etc.)

    If you go with striping drives, it does improve speed. The trade off is that if a drive fails, all data is lost in that raid. This suggests that you consider external back up of the same size of space available internal to your Mac Pro.

    Apple also sells an expensive Raid card meant to work with your internal drives and gets fair results in raid 5. I am unsure about EFI updates.

    Beyond raid - handling large files can really slow down your system as they can frag a drive. No matter what people way about OSX not needing to be defragged, it does suffer. The more volume of your drive taken up and non contiguous the harder your drive has to work. You can elect to defrag your drive(s) from time to time, or if you have a full bootable back up you can restore it to your drive(s) which in effect does what defrag does. The latter method might be called "repacking" your drive.

    Tools you might investigate
    Retrospect and Superduper (backup software)

    As for raid, as I sad, lots of options available and yes raid can do a great deal to speed up systems or at least reduce the threshold for things that start slowing your system down.

    Hope this is fair food for thought.
  3. nanofrog macrumors G4

    May 6, 2008
    Nice post prehdd. :)

    ceres, beyond what prehdd listed, you'd have to use some level of hardware RAID. From a simple controller using software RAID (also called Fake RAID), to a full RAID controller that contains its own cache and processor.

    You could mount a drive in the empty optical bay and use it as an OS drive, and run the array (RAID set) from the drive bays. Other types also can become available, such as RAID 0/1/10/5/50/6/60, depending on the RAID controller used. Levels 1/10/5/50/6/60 give you some degree of redundancy, but 5/50/6/60 can't be had from OS X alone.
  4. ceres thread starter macrumors regular

    Nov 14, 2007
    Dark Forests of Germania
    From what I have read Apple´s Raid Card doesn´t support Windows and is too expensive for the speed it can provide. I have read the info on barefeats and elsewhere and it appears that the Highpoint 2640/80 are worth looking into,
    From what I have gathered it is not possible to create a single Raid 5 Array, and use it as a OS X Bootdrive with Vista 64 or 7(whenever it comes out) as a Boot Camp Partition on the same RAID while maintaing the ability to update EFI.
    Hence I will need, as nanofrog pointed out, an additional Boot Drive mounted in the optical bay to serve that function. Applications and a seperate Boot Camp Partition will reside on the RAID.
    What about fragmentation of the RAID? Is it as much of an issue as under a non RAID HDD to Mainboard Controller setup?
    The 2640 is a mere 150 Euros while Apple´s less performant card comes in at 600 Euros. Is there any justification to Apple´s card?

  5. nanofrog macrumors G4

    May 6, 2008
    Apple's card only works in OS X. :(
    You can get a lot more card for the money, barefeats and others have demonstrated this.

    Personally, I do think fragmentation should be addressed on a RAID array. Others may not.

    Apple vs. the RR2600 series, the Apple really isn't the way to go. The RR2600 series is actually fake RAID. It uses software with a SAS controller, and uses the CPU to perform the processing. No cache, or processor. Just check the card images on HighPoint's site.

    And it still outperforms the Apple RAID card despite the fact it does have cache and a processor on board! :eek: :p
  6. ceres thread starter macrumors regular

    Nov 14, 2007
    Dark Forests of Germania
    Thanks nanofrog!
    Would you say that the concrete setup I outlined above will work?
    Would buying a more sophisticated Highpoint controller yield tangible perfomance increases? I might be interested in the option to add (later on) an external 4*SATA enclosure to complement the internal 4*SATA RAID Volume (maybe for Windows7). So I´d need a card that can manage 4 internal and 4 external drives. Is there a winner in HighPoints range?
  7. phrehdd macrumors 68040


    Oct 25, 2008
    Let's be clear here. Apple offers software raid (no raid 5/6). Apple hardware raid offers raid 5. Other raid cards perform as well and better than Apple's hardware raid. I don't think anyone disagrees (and I did say Apple's card gets "fair" results in raid 5).

    Question - Apple software raid and Hardware raid take advantage of drives that are internal to the Mac Pro - what 3rd party raid card can engage all four internal drives of the Mac Pro?

    AMUG offers some nice reviews of raid cards. There tests are a good combo of stat data and real world usage scenarios.

    If money is not an issue - I have to agree, get a good raid card, get a nice box to hold 5-8 drives and select the raid of your choice be it slower raid 3/5/6 or just stripe the drives for max speed. Of course you could get 8 drives, mirror 1:1 drives and then stripe them for almost straight stripe performance and be a bit safer but only the volume of 4 drives. As for booting to Windows..this was not in the original post as a criteria. Depending on what you are doing, there is virtual options - VMware Fusion and Parallels for Windows usage.
    Again - if its speed and you want to use the internal drives only you are limited, if you can afford thinking/spending "outside the box" get a raid card and an external raid box.
  8. nanofrog macrumors G4

    May 6, 2008
    I'm not saying Apple's RAID card is useless, just that it's limited for the money. For $800, I can buy an Areca ARC-1680ix12. More cache and upgradeable, faster processor (IOP 348 @ 1200MHz), capable of running RAID 0/1/10/5/50/6/60, works with Boot Camp, can run 128 drives using SAS expanders, and more ports. (Can be had for ~$769 from

    There's a few cards on the market that work in Mac (as in accept the iPass cable from the drives), some even with Boot Camp.

    Off the top of my head, the following manufacturers using internal iPass (SFF-8087) ports and are Mac compatible:

    Areca (ARC-1680 series, SAS & work with Mac) other SATA models too
    HighPoint (RR4320 true SAS RAID; RR2680 uses 2 internal iPass connectors, fake RAID; no multiple OS's on HighPoint cards)
    Atto Technology (R348 configurable hybrid)

    Others that offer SATA cards with internal iPass connections that work in Macs:

    Individual needs and budgets always apply of course, but there are at least a few different cards to chose from. ;)

    As for raw speed with no worries over redundancy, and only using the internal bays in a Mac Pro, the best I can think of ATM, would be a RAID 0 using 4x Seagate 15K.6 SAS drives. They have a sustained transfer rate of 164MB/s, so ~650MB/s that way. :eek: :p
  9. phrehdd macrumors 68040


    Oct 25, 2008
    All very interesting and informative. Thanks. One day I'll be rich enough to afford a 600 buck card, multiple SAS drives and have some fun. <G>
  10. nanofrog macrumors G4

    May 6, 2008
    Definitely not on the cheap side. :p

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