Bootable RAID 5 -- Part Deux!

Discussion in 'Mac Pro' started by timb, Nov 28, 2006.

  1. timb macrumors regular

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    #1
    So, I held out until the Intel Xserves were released but... a RAID card from Apple was conspicuously absent... It seems that there are still no bootable RAID 5 solutions for the mac pro (either SATA or eSATA).

    Perhaps I'm missing something? Has anyone seen or heard of anything that would get this job done?

    -timb
     
  2. livingfortoday macrumors 68030

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    #2
    RocketRAID cards claim to have bootable disk support. There's this one here, for example:
    http://www.highpoint-tech.com/USA/rr1820a.htm

    It's OS X compatible, does RAID 5, and is bootable. I haven't looked at their other offerings, but they probably have what you're looking for (MacPro compatible, in other words).
     
  3. timb thread starter macrumors regular

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    #3
    AFAIK those are bootable only on PCs. (BIOS vs EFI thing.)
     
  4. Sesshi macrumors G3

    Sesshi

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    #4
    Can't you boot from the Fibre Channel card (besides asking why you would so want to boot from a RAID5 array)?
     
  5. timb thread starter macrumors regular

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    #5
    Why wouldn't you want to boot from a RAID-5 array?
     
  6. Sesshi macrumors G3

    Sesshi

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    #6
    Because the boot drive would usually be the drive with the most random transactional use on a workstation. Depending on the card / DAS / SAN, the transactional & performance overheads of RAID5 vs RAID0 for an easily backed up boot drive / array isn't in most cases an effective tradeoff for a high-performance workstation.

    If it's a server, sure. But if it's a workstation - unless constant uptime is more important than performance - you only really need to keep data on a RAID5 DAS / SAN, and backup the boot drive/array properly.

    Since the Mac Pro isn't quite as flexible as a real workstation (no SAS support out of the box, etc) and falls more into overpowered desktop territory that's what I bought/use it as - Now I just have 10K drives in RAID0. However on my Windows workstations I have 15K SAS drives in RAID0 and the PC's themselves connected to a RAID5 SAN, which is the optimum configuration for performance + safeguard of data. A similar but lower-performance combo is possible using XServe RAID in RAID5 / Pro + 10K SATA striping, which would offer best-as-possible Pro performance along with data protection.

    On a tangent but I'm pretty surprised by pricing for Xserve RAIDs as I was initially by the Pro, very tempting indeed especially as they're purported to be cross-platform.
     
  7. timb thread starter macrumors regular

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    #7
    That's true in a lot of cases I suppose.

    Though I've found RAID-5 to write nearly as fast as RAID-0 using a card with the proper amount of cache RAM on it. Read speeds tend to slightly edge out RAID-0, in addition to the decrease in risk.

    I suppose I could live with RAID 0+1 if I had to... That can't be done via software can it? (I.E. Can you Apple RAID 1 a Apple RAID 0 volume?)

    Anyway, there are multiple reasons a bootable RAID-5 array is ideal for me in this situation, and multiple reasons why SAS or NAS aren't.
     
  8. rsvrmille macrumors newbie

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    Sep 2, 2006
    #8
    apple raid

    can do raid 1, 0 or 0+1.

    for 0+1 in disk utility (boot from the dvd is easiest) create two raid 0 arrays "raid 1" (disk 1+2) and "raid 2" (disk 3+4), then create a third array dragging "raid 1" and "raid 2" and set them to be mirrrored. Voila, raid 0+1.
     
  9. timb thread starter macrumors regular

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    #9
    I wonder what the performance implications of doing this are? If it's not bad I might grab 4 10k RPM drives and do this.
     
  10. Sesshi macrumors G3

    Sesshi

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    #10
    Well... you're almost doubling disk throughput by going RAID0 per set of disks but then you're more than halving it by the overhead of going software RAID 1. You're probably looking at about one unRAIDed disk's throughput in all.
     
  11. foo.c macrumors newbie

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    #11
    Not according to this.

    http://macprojournal.com/soft-raid.html
     
  12. Sesshi macrumors G3

    Sesshi

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    #12
    I just skimmed that... but from what I could make out, it's even worse? :eek:

    (Bearing in mind a 3Gb test file is hardly a realistic - nay, rather optimal test)

    As the original poster seems to be aware in any case, anything beyond RAID0 (and even that really) is best achieved with a dedicated card if performance means anything to you. But that's not welcome news from the looks of it.
     
  13. foo.c macrumors newbie

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    #13
    Looks like the RAID10 setup is a good percentage faster than a singleton. Unless I read it wrong ... longer bars are better.
     
  14. timb thread starter macrumors regular

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    #14
    Yea, from that it looks like a single disk reads at around 60 and a RAID 10 set reads at 180, which is about what I'd expect from a stripe of mirrors. If you set up RAID 01 (which is a mirror of stripes) you should be able to get a read of 180x2. (At least in theory.)

    Incidentally Mac OS X does do software RAID 01 as well as 10. 01 has less fault tolerance though. (It can only survive one disk failure, whereas 10 can *sometimes* survive two.)
     
  15. Sesshi macrumors G3

    Sesshi

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  16. timb thread starter macrumors regular

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    #16
    I just got around to ordering 4 Seagate 7200.10 250 GB drives. They're 7200 RPM, but I got them for $75 each. I just couldn't justify spending $250 *per drive* on the 150 GB 10k Raptors. I did a little research, and these 7200.10's are very competitive.

    I'll be hooking them up in RAID 10. When I do I'll post the results.
     
  17. superbovine macrumors 68030

    superbovine

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    #17
    I wouldn't mind seeing the performance of a SAS controller on apple's desktops. I believe xservers have SAS raid out of the box.
     
  18. timb thread starter macrumors regular

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    #18
    Drives should get here tomorrow. I will do before and after benchmarks with Bonnie.
     
  19. timb thread starter macrumors regular

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    #19
    Okay, so did a test with just the single, stock WD2500JS.

    It's clocking in at around 52MB/s write, 54MB/s read. (Sequential)
     

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