Protecting 4xWD640 RAID 0 with external drives- Any advice appreciated.

Discussion in 'Mac Pro' started by mgsarch, Mar 26, 2008.

  1. mgsarch macrumors regular

    Jan 19, 2008
    I have a 8-core MP 2.8Ghz with 10gb ram and Ati 2600HD. I'll someday replace the ATI with a quadro (all my application is 3d/CAD/Design) I'm installing 4 of the WD640 drives, they arrive on Friday.

    I would love to order the CalDigit RAID card but after searching I finally figured out it's not available until next month.

    That said, I need my system to start working ASAP and I don't want to wait if I don't have to.

    I'm a designer, I need fast scratch so some striping needs to be involved. I also need data protection. At this capacity Time Machine isn't going to be of any use and I'd prefer redundancy anyway.

    The 4 WD640s are replacing: 1 750gb 7200.11, 2 WD SE16 500GBs, and 1 320GB (Apple Stock Drive).

    I would like to sell some of those drives to defray the cost of this endeavor but I'm open to keeping 1 or possibly 2 as external drives or stuffing one into the optical bay with a converter.

    I want speed and reliability, of course! :) But really the largest motivator here is the combined drive aspect. Having so many volumes is driving me nuts.

    My intention had been RAID 5 or 6 but I now know that Apple Software RAID can't do this. So now it seems with software RAID 0+1 would be the only option.

    Realistically, does the cpu performance degradation outweight the speed gained from striping the drives? It's so difficult to determine bottlenecks.

    Any thoughts on my best bet without/before the RAID card arrives. Can I migrate the array after installing the card without data loss?

    If I just JBOD the drives can the concatenated set be broken up ever? I was thinking I could JBOD until the card came.
  2. davepk macrumors member

    Nov 20, 2006
    Software Raid0 the 4 new drives and keep the 750 as a bootable clone and TM storage.

    Chances are you'll split the raid0 into 2 partitions. One for OSX + Apps etc, the other as scratch/misc none critical etc.

    The 750 should be more than enough as a clone plus TM.
  3. mgsarch thread starter macrumors regular

    Jan 19, 2008
    so be it. haha.

    any tips for migration from the 4 existing drives? i'm picturing fw800/usb2 enclosures :\
  4. mgsarch thread starter macrumors regular

    Jan 19, 2008
    I am initializing the 4 WD's now and I have the 750 plugged into the FW800 port.

    I created a 2.3TB array with the 4 640s and I'm allowing Disk Utility to write 1 pass of zeros to array. I generally don't even bother but the striping has me thinking it can't hurt to let diskutil see all the blocks before moving forward.

    Once this is done I'm thinking that I'll partition the array just as you suggest- 500GB/750GB for the boot partition and the rest for scratch and misc storage.

    Few things I'm still questioning-

    Most Important:

    1. WDTLER Utility- Do I need to use that on these drives? TLER should be on by default since these are desktop drives. I assume I want to turn this off since the four drives are striped?

    Other Questions:

    2. CPU degradation from the software RAID.

    3. Optimal External Setup For Backup
    -If I use the 750GB Seagate, Should my boot partition be 750GB as well?
    -How will this integrate with Time Machine? Am I better off
    keeping 1 of the 500GB externals to use as a dedicated
    time machine drive and then using the 750 as a clone of
    the boot?

    If the 750 were to act as both the clone and time machine, would I partition the 750 to reflect those two functions?

    Sorry to be needy, I'm just wary of my data being striped and I want to take proper precaution. Thank you so much!
  5. overcast macrumors 6502a

    Jun 27, 2007
    Rochester, NY
    Why don't you RAID1 on 2 drives, and RAID0 the scratch on the remaining two. When your RAID card shows up, convert the 4 disks to RAID 10. Unless you absolutely need 2TB of space, this seems like the logical way.
  6. mgsarch thread starter macrumors regular

    Jan 19, 2008
    So essentially, 640GB OS/Apps/Critial Data + 1.3TB Striped Scratch?

    Instead of RAID1 might it make more sense to just stripe 3 drives and Clone the 640 to an external? time machine?

    hmmm ....

    Definitely logical. I'm being greedy and wanting the performance from the striped boot drive. I was hoping that between Time Machine and a bootable external I could mitigate the risk of the 4 drives being striped.
  7. overcast macrumors 6502a

    Jun 27, 2007
    Rochester, NY
    You aren't going to notice a striped OS drive. You'll gain the benefit of RAID1 when doing multiple disk accesses anyhow. And your critical information will be protected from disk failure. If you want to deal with recovering from Time Machine, then go for it. Just keep in mind, each drive you add to a striped array exponentially increases your chances of a drive failure wiping it out.
  8. mgsarch thread starter macrumors regular

    Jan 19, 2008
    Point taken. : )

    BOOT- 640GB RAID1

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