Software RAID versus hardware RAID

Discussion in 'Mac Pro' started by strausd, Apr 20, 2010.

  1. macrumors 68030

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    #1
    Hey guys, I am planning on getting a 2010 MP when they come and have a question about it. I am 90% sure that with my budget, I will not be able to after a RAID card. I am wondering if software RAID would be alright or if it's so bad it's not worth doing. Also, there is small chance that I could buy a RAID card later on, how would I install it? I will be using it for 3D animation with Maya and some zbrush modeling. Also I will be doing some Photoshop and illustrator and maybe some gaming on win 7 boot camp. Feel free to list any other pros and cons about either a software RAID or hardware RAID, I wana make sure I have all the details before making a final decision on it. Thanks for all the help in advance!
     
  2. macrumors 65816

    Decrepit

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    #2
    My recommendation would be to just do software raid 0 for highest performance AND BACK UP BACK UP BACK UP BACK UP BACK UP.

    And BACK UP.

    With Time Machine, you can be backing up to another location at your place. You might consider a second backup program that backs up your data to another location/site. If it's really important, make sure you can get it back even if your house burns down.

    You don't need to be able to recover your operating system in a catastrophic event. You can go buy another Mac Pro with your insurance check. But your data is priceless, so it should be kept in at least two locations.
     
  3. thread starter macrumors 68030

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    #3
    What are the cons of a software RAID and how is it done?
     
  4. macrumors 65816

    Decrepit

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    #4
    I haven't been able to try it on a Mac yet, my experience comes from the server world.

    But software RAID basically means that the computer handles the splitting up of the files instead of a dedicated controller.

    Hardware is the only way to go for important arrays. RAID 5, 6, etc. But for straight performance, there's no math involved, so the CPU can handle it.

    One of the resident Mac Pro owners will be able to give you an easy rundown.

    But in case I didn't mention it before, do your backups, and don't just rely on Time Machine. Time Machine is awesome. But it doesn't offer you offsite recovery. If you're spending the cash on a Mac Pro for real work, do the homework on a backup solution.
     
  5. macrumors 6502

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    #5
    plenty of spare cores

    Assuming the 2010 Pro has 12 or 6 cores, there are plenty to spare to cope with the overhead of software raid. One thing that more expensive raid cards have is large buffers. I don't know if the software raid uses RAM as a buffer in the same way - I'd assume it does. I've been told that for a powerful workstation like the Mac Pro with plenty of cores and RAM, software raid is as good, or even better, than hardware raid (certainly for raid 0).
     
  6. macrumors 6502a

    Angelo95210

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    #6
    Software backup is recommended in case you need to start up quickly after an incident like a hd crash. It's not a backup solution as you know, so I would go for two spare hd drives for backup, one with TM the second one with SuperDuper or CarbonCopyCloner.
     
  7. thread starter macrumors 68030

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    #7
    How do you even do a software RAID on a Mac Pro?
     
  8. macrumors 68040

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    #8
    It is easy to set up is Disk Utility. I am all software RAID on my systems, never had an issue.

    I have RAID 5 systems, but they are all external. Anything actually in the machines are simple stripes.
     
  9. thread starter macrumors 68030

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    #9
    Would a software RAID 0 be just as fast as a hardware RAID 0?
     
  10. macrumors 6502

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    Jul 14, 2007
    #10
    before you install mac os x you have to configure the raid. I haven't been able to figure it out an existing install. You can redo it from time machine though. You go into disk util when you boot off the install disk, you create the mirror raid then drag to two disks to the raid, then you install the os.

    If the raid breaks, you have to boot off the install disk and open up disk util and it'll start repairing (which will take a long time, over night usually).

    It works fairly well, its worth it since reinstalling from time machine can take over night.
     
  11. macrumors G4

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    #11
    Software implementations of parity arrays = Really Bad Idea, as it can't handle the write hole issue. Hardware controllers use an NVRAM solution in conjunction with a card battery to solve it.

    And a UPS is a necessity as well (and does more than the card battery). Ideally, you run both (UPS + card battery), but I've seen budget restrictions far too often, and if you're forced to only get one, go for the UPS.

    Even in the enterprise world, the card battery is typically skipped, but the power systems implemented are far more extensive than just a UPS as well (redundant UPS + redundant generators; n+1 configuration at a minimum).

    Not quite. A stripe set is a low demand form of RAID on the processor, but the cache on the hardware cards can make a difference, and with some cards (expandable cache), it's quite notable.

    But there's a notable cost difference as well. Not just for the card, but you typically have to run enterprise HDD's rather than consumer models (which can be used in a software RAID, as the control is retained by the system rather than the card). So the recovery timings in the consumer models will work.

    That said, enterprise drives are a good idea anyway, as they're rated better, and have additional sensors that prevent the heads from physically crashing into the platters.

    You can't, as the inititalization process "carves" the disks up into stripes. In doing so, any existing data on them is destroyed.
     
  12. macrumors 68040

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    #12
    I thought I said this, but I guess not. I only run software stripes, which run fine for me. All of the RAID5 systems are external with their own controllers.

    I think it is fine to run a software mirror, but anything more extensive should probably be hardware.
     
  13. macrumors G4

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    #13
    Software can function correctly for 0/1/10, though there are reasons for using a hardware controller for these levels as well (but it's not always a necessity, and dependent on the specifics).

    It's parity levels that software hasn't the full ability to operate properly. When you say the externals have their own controllers, what are they?
    eSATA based?
    Proper hardware RAID cards?
    Or is it a board in the enclosure itself (can be problematic, and really has to be investigated properly)?

    Just curious, as you could be less protected than you think.
     
  14. Rad
    macrumors regular

    Joined:
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    #14
    3 1/2 years without a problem

    I have been running a Apple software RAID 0 with internal WD Raptors since August 2006 in my first generation Mac Pro. I use the computer extensively for both work and play. I have never had a single problem for the entire time - over 3 1/2 years. I do have a regularly updated backup drive via Super Duper. Easy, inexpensive and very fast.
     
  15. macrumors 68040

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    #15
    I have and continue to buy these, three at a time. Of each triplicate, one is operational, one is onsite backup, and one is offsite backup. Each changes place every week or so. I think I am going to be okay. :) However, I do want to kiss whomever came up with quick release rack pins!

    For the stuff where speed is not important and data amounts are smaller, I get these in triplicate, same deal as the above, just much easier to move around.

    I hope OWC appreciates the amount of business I throw at them!
     
  16. thread starter macrumors 68030

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    #16
    What about a software RAID 0 on 2 drives and use time machine to back that up? Is an offsite backup necessary or just a good suggestion?
     
  17. macrumors 68040

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    #17
    I would say that would be fine. That is what I do with my system SSDs. There is not really a need to have a full OS backup these days unless you are concerned about uptime.

    The bottom line about backing up is that you can never be paranoid enough. Get to a point where you are comfortable (and your data is safe). Hardware pooping out and damage or theft are different issues. I would always recommend having an offsite backup of at least important personal/work files, but that is probably way overkill for most.
     
  18. thread starter macrumors 68030

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    #18
    I think that my most important files and documents will be on my MBP as well which I take everywhere. So in a way it's kind of like an offsite backup. I am planning on not having a SSD as my boot disk because there will be a lot of OS X applications I will be putting on there along with windows 7 boot camp and programs for that. So it seems like there may not be enough space on a SSD for all of that, if there is I don't think my budget will be able to handle it :(
     
  19. thread starter macrumors 68030

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    #19
    Also, what kind of performance decrease would I see if i had 2 drive (not my boot drive) on software RAID 0? These drives would hold my 3D documents, animations, and psd's
     
  20. macrumors G4

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    #20
    Both use Oxford 936 chips (different variants), but are hardware controller SoC's (use ARM processors). So you're definitely better off. :)

    Compared to a single disk (HDD) or SSD?

    With a stripe set, the throughput = n* the throughput of a single drive. So for n = 2, it's 2x faster than one of the disks used on it's own. This applies to both mechanical or flash, but with flash, you can run into bandwidth issues (aka throttling, but it depends on the specifics, such as how many drives in the set, how many on the same controller, and whether or not they're used simultaneously).
     
  21. thread starter macrumors 68030

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  22. macrumors G4

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    #22
    Mechanical stripe sets are faster at sequential throughputs, and slightly at random access (theoretically, it halves, but that's rarely the case, as there's mulitple dependencies that just aren't met under real world conditions).

    But it's also less expensive than an SSD, especially when you look at it from a cost/GB POV.
     
  23. thread starter macrumors 68030

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    #23
    How difficult is it, if at all, to install a RAID card yourself? There is a chance that I can maybe afford one later during the year
     
  24. macrumors G4

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    #24
    Not difficult at all. Just be sure to read the manual carefully, if you're not that confident about it.

    Basically, you plug the card in, attach the drives, and fire up the system. Install the drivers, then gain access to the card, and create the array.

    But personally, I add a step before creating the array, and that's run a full surface scan of the drives (new or not), to get an idea of the drive's health (i.e. helps find damage due to either poor QC or shipping). Age as well, if they're used.

    Once the array is created, then you can transfer data to it. If it's the OS, you re-install from a clone (assuming you've a spare disk for this task, and install the drivers if the clone is made prior to driver installation), or do a clean install if there's no spare drive you can use.
     
  25. Loa
    macrumors 65816

    Loa

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    Location:
    Québec
    #25
    Did you skip a word between "slightly" and "at", or are you implying that RAIDs of mechanical drives are faster at random access than SSDs?

    In my 2009MP, I saw just about the same speed increase going (for my boot volume) from a 4 disk RAID0 to a single SSD, than I saw going from a single mechanical drive to that 4 disk RAID0. (In other words: single HD < 4 disk RAID0 < single SSD)

    Isn't random access the defining factor for an OS volume?

    Loa
     

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