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Thread: Boot from RAID?

  1. #1
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    Traveling through the forums - mainly SCSI and RAID - during the last few months, I recall that some members recommend not booting from a SCSI RAID.

    Why not?

    Just to clarify:

    мя G4 466 or newer
    мя Gurus SCSI setup - ATTO UL3S, Cheetahs, Granite cable/termination, etc - internal.
    мя OS 9.1 plus SoftRAID, or 10.1.x native RAID (both mirrors)

    I have two Macs (both 9.1)booting to the RAID mirrors now with now apparent problem, and setting up one for OS X. Is this a bad idea?

    ------------------

  2. #2
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    I think most of the issues would have been with booting from software striped volumes since building the stripe takes installing the software which comes in the middle or end of the boot process. Untill the stripe is built the volume is unreadable.

    Your mirror needs no raid software to be readable from the boot drive/volume half of the raid.

    Rick

  3. #3
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    I have been told you can boot of a raid 1. It is unsupported but it works.

    Other than that, a hardware raid setup is the only other choice if you need to boot of a raid.

    George

  4. #4
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    My 9500 G3-400 boots MacOS 8.6 and 9.1 from a Miles2 controlling two IBM LVD 18g drives in a striped SoftRaid 2.2. I've had no problems I can ascribe to the RAID0.

    9.1 boots in 2/3 the time of an ATA100 drive on the same machine.

    ------------------
    ricercar

    my free 9500 is nickel-and-diming me to death!

  5. #5
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    On my 7300 (using either the OEM 2940U2B or ATTO UL3S) I can boot from stripped raid fine. But on NewWorld B&W only able to boot from mirrored volume. I think sometimes around G4/AGP (maybe even with the Sawtooth) changes to OpenFirmware killed that too?

    Gregory

  6. #6
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    kaye knows this one. I believe the limitation is that you cannot boot from a RAID 1 in certain types of machine, and that New World machines cannot boot RAIDs at all due to something in the boot process. Mag has booted Beast from a monster RAID 0 for years.

    Batsignal invoked to kaye!

  7. #7
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    The deal with boot ROMs and New World macs is the removal of most of the Boot ROM to the hard drive. ROMs are slow and expensive so Apple moved all but the most basic boot up instructions to the hard drive which gets loaded into ram where it is much faster.

    This is also why there are few ROM flash revisions from Apple, they can change the important parts of the Boot from a OS upgrade. No need to flash upgrade the New World ROM when all that's on the ROM is the very basic instructions on how to load the Bootstrap program from hard drive or CD.

    Kaye'l have to check me on this, but I think the reason that New World computers are unable to boot from software raid is that the simple rom instructions are not enough to form the raid volumes and access the rest of the rom data that's in the system folder. Chicken or the egg type problem: The rom can't load cause the volume can't mount till the roms been loaded.

    Rick

  8. #8
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    Two things going on here but I am no expert on this. As Rick and Ripper say the New World Macs won't boot from striped RAID (RAID 0). Other than striped RAID, other types may work, as many of you have found.

    Ripper brings up another point about vintage Macs with a lot of PCI cards (6-slot Macs) that Darin first discovered with his 9600 Kansas machine, three monitors, xlr8 g3-500 I think, dual Miles2, all PCI slots full. There is a 4MB limit in something that is needed for the boot process (I forget what it is technically called) which, if exceeded, will cause a no boot situation, no matter what you are booting from. The solution was to create a small HFS (not HFS+) striped boot partition and then he could boot off of striped RAID. The reason this worked is that the HFS info in the 4MB takes up less space than HFS+ info, so he was now under 4MB. k

  9. #9
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    There is a 4MB limit on B&W G3 as well that prevented using three SCSI cards (ATTO UL3S, two 2940U2B) according to Mark James, this is just one of the limitations in the Blue G3 line.

    Interesting work around though! And weird. Computers need a psychologist - for all their "personality disorders" and I wonder (doubt) that all the "Sad Mac" troubleshooting books have filtered through all that into digestible form. And to think users have to learn the hard way and contend with all this lore.

    ATTO won't RMA my UL3S. Say "it works in a stock supported configurated machine" but not in a Blue G3 running 9.2 etc and they would use a different firmware (and flash process?) than I would use. Unfair playing rules.

    I was misled that Macs are plug and play and only PCs were "plug and pray."

    Gregory

  10. #10
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    Did you buy it here? If so you can return it if it's been less than 30 days.

    If you didn't buy it here, you should have........

    Regards,

    c8

  11. #11
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    Proud to say all the SCSI related stuff I have purchased for my employer has come from the Gurus. . .

    Thanks for all the info (even the stuff that is over my head :0). So, to summerize, if the machine boots and is happy (mine is), I have nothing to worry about?

    BTW, I have in the past I had a BW 350 that would not boot propoerly to RAID 1 (same SCSI setup), unless I booted with extesnions off. Finally gave up on the G3 thinking it was SCSI voodoo,and switched to the current G4 400 (sorry, not the 466 I listed in the original post). Started booting to the SoftRAID drives about a month ago, with no problems.

  12. #12
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    Proud to say all the SCSI related stuff I have purchased for my employer has come from the Gurus. . .

    Thanks for all the info (even the stuff that is over my head ). So, to summerize, if the machine boots and is happy (mine is), I have nothing to worry about?

    BTW, I have in the past I had a BW 350 that would not boot propoerly to RAID 1 (same SCSI setup), unless I booted with extesnions off. Finally gave up on the G3 thinking it was SCSI voodoo,and switched to the current G4 400 (sorry, not the 466 I listed in the original post). Started booting to the SoftRAID drives about a month ago, with no problems.

    [This message has been edited by newbie (edited 28 January 2002).]

  13. #13
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    I have in the past I had a BW 350 that would not boot propoerly to RAID 1

    The main issue is (was?) booting off RAID-0 (stripe) and there were several cases where it was problematic booting off RAID-1 (mirror). Never assume. It really depends on HOW IMPORTANT IS YOU DATA?

    WHAT WILL HAPPEN WHEN YOUR RAID dies?
    Is everything BACKED UP?
    Twice?

    Seagates are rock solid, but nothing lasts forever, nor is ANYTHING perfect.

    ------------------
    I'm back!

  14. #14
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    All data is transfered daily to the internal ATA drive, and then the ATA drive is backed up to VXA tape via Retrospect network. I have recently installed the email server app on my machine, so I can transfer all of the backed-up user data and easily verify/restore files (as it is all encrypted by the app FirstClass Server 6.1), without taking the working server offline. Wish I would have thought of this a year ago. . .

    The machine boots fine and is more stable with the SoftRAID drivers than with the Apple drivers previously used.

  15. #15
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    I have a RAID0 on my B&W so after reading this, ran OS 9.2.1 installer, then update to 9.2.2.

    With this being the only volume, it boots after searching. Never had trouble with mirrored volumes using SoftRAID (and I agree that I prefer it over any other - though I do use FWB HDT for its mode page restore and optimization routines now).

    Odd that with OS X on a partitioned SoftRAID volume (1st), I've got some OpenFirmware type problem or something. Startup Disk isn't seeing that drive (internal), just the stripe raid (external). They are all on, unique ID etc.

    I'd say something is "not kosher" (ie, hosed) and switing in/out of OS X isn't supported. Maybe because of the SoftRAID. (OS X strips out the driver when installed). I have to just to see what happens.

    Gregory

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