RAID as statup volume?

Discussion in 'General Mac Discussion' started by kgarner, Oct 15, 2004.

  1. kgarner macrumors 68000


    Jan 28, 2004
    I have tried looking around for info on this but haven't found a definitive answer. Can I make a RAID set my startup volume? Any precautions to be wary of? Can I RAID a 30 GB and 40 GB together or do they have to be the same size? Thanks for the info.

    PS using the Disk Utility software RAID setup in Panther. I am planning to stripe in order to have the two act as one drive.
  2. benpatient macrumors 68000

    Nov 4, 2003
    well, you can on a G5 using SATA...I did it no problem straight out of the box....well, it took me a while to figure out how to Disc Utility to let me create the array, but my RAID 0 array has been perfect since day 1.

    320GB of 100MB/Second joy.

    I'm not sure if you can boot to PATA RAID arrays or not...not even sure it will let you make one...but you're talking about 30 and 40 Gb drives...which says to me that you aren't talking about SATA.

    as to the size of the discs and what you get for striping, no, they don't have to be the same size, but it will use the least common denominator. Example:

    30gb drive and 200 gb drive will create a RAID 0 array of ~60gb, or a RAID 1 array of ~30gb.

    The rest of the space will be wasted. It's possible, I think, to create a partition on the larger drive to offset this wasted space, but I'm not sure that it's a good idea, because at that point, you're taking a virtual drive spread over 2 physical drives and adding another virtual drive's worth of complication into the mix. Talk about asking for catastrophic data loss!

    I'm not sure you can do RAID 0 without a physical RAID controller card on standard PATA drives, anyway.
  3. slooksterPSV macrumors 68030


    Apr 17, 2004
    Did you try looking in the Startup Dialog? I'm not sure if that helps, but its worth a try to see if it will work.
  4. csubear macrumors 6502a


    Aug 22, 2003
    Yes, You can with PATA. No worrys. Everything works just fine.
  5. psycho bob macrumors 6502a

    psycho bob

    Oct 25, 2003
    Leeds, England
    If you are serious about RAID get a PCI controller card (like seritek etc) and connect both drives to that. Using any form of software RAID incurs a CPU performance penalty as it is the processor that has to take charge of splitting the data up and also collecting it again from both drives. I had a RAID 0 set in my G5 at first but you really pay the penalty if you are running something CPU intensive and then just try to use the finder. I now use a 10K Raptor as a boot and program drive and place my home folders contents on a second drive. I was pleasantly suprised to find this far faster. Unless you choose hard drives very carefully and set it up right a Raptor will be faster for most things then a RAID 0 set of 7200rpm hard drives. If you have a dual CPU system then the processor hit may be worth it to you if you don't or have a slower dual like an early G4 I would forget about it at least as a boot/system/home combination.
    If you have two separate drives with your work on one then with a G5 at least you can take advantage of both separate SATA buses. You can open programs while saving your data without having the system grind to a halt, even RAID won't help there. RAID is best left for gamers who can risk everything for the sake of maximum performance and as scratch volumes for FCP and PS.
  6. MacsRgr8 macrumors 604


    Sep 8, 2002
    The Netherlands
    I have tried it on a B&W G3, but it couldn't boot.
    I put two identical 10 GB drives in it, and set the RAID as stripe. The Disk Utility could choose the RAID as Startup Volume, but the B&W G3 never booted from it.

    I have also tried the RAID 0 scheme on an Xserve Single 1.0 GHz G4 with two 120 GB drives. That was no problem.
    These drives are all "masters" but I don't think that is the issue here.
    Maybe a minimum of ATA-100 is needed for RAID booting compatibility?

    Any ideas?
  7. EminenceGrise macrumors member

    Jun 23, 2004
    When you say all the drives are 'masters', what do you mean? If you have both drives connected to the same IDE bus (both are attached to the same cable), one of the drives must be set to 'master' and the other 'slave'. You can't have two masters on the same bus - it will either not work at all, or not work right. If that's the case, fix that and it may well work.


    It might be an OpenFirmware issue - the B&W G3 is an 'older' machine. In other words, OS X might create the RAID and see it just fine, but the OpenFirmware revision in the B&W G3 doesn't know how to boot from it. I don't think there's much you can do about this unless there is an OF update from Apple.
  8. MacsRgr8 macrumors 604


    Sep 8, 2002
    The Netherlands
    An Xserve G4 has 4 seperate ATA-100 busses.

    So all connected drives in their bays are set to master (one HD per bus).
    IMHO that is not the issue regarding bootable "soft" RAID.

    I agree about the OpenFirmware. It could be necessary that the Mac should have the newer types of OpenFirmware (say the Target-disk mode compatibility) for RAID booting to be possible.

    Interesting to find out the the oldest Mac capable of RAID booting?

    "Newer OpenFirmware?' : Sawtooth G4 and higher?
    "ATA - 100 bus?" : MDD G4 and higher?

    Nice to find out. :)
  9. EminenceGrise macrumors member

    Jun 23, 2004
    Ah, I see, I had somewhat misread your original post. The way I read it I wasn't sure if you were saying the drives in the B&W G3 had both been set to 'master'; this would cause problems if they were attached to the same bus. Anyhow, I agree that whether the drive is set to master or slave should not be an issue for software RAID.

    It would appear that the issue is the B&W G3 ROM, according to Apple:

    They give a workaround, but not a fix (create a small mirrored partition across the two disks to boot from, then allocate the remaining space as RAID 0).

    Also seems to affect the PowerMac G4 ('original' only?):
  10. MacsRgr8 macrumors 604


    Sep 8, 2002
    The Netherlands

    Tnx for the links.

    Stil a nice one to figure out which G4s will boot from a RAID....
  11. aplasticspork macrumors regular

    May 27, 2004
    Seattle Wa.
    i tried to RAID two LaCie 160 Gb disks together (completely identical disks) with my iMac G4 and it couldnt boot :rolleyes: i wish it had worked though cuz the system installed in about 30 minutes as opposed to two hours on the internal drive :)

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