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Thread: live software raid

  1. #1

    Default live software raid

    First of all, apologies if this is posted in the wrong forum. I didn't see one that was more appropriate.

    I have a win7 PC running Nvidia raid 10. Yes, I know this is not a win 7 forum, but I'm getting to that. The PC hardware runs opensuse 64 bit 11.3 just fine. I had it set up in raid 0. The motherboard on my win 7 PC died, so I pulled all the drives (four since it is mirrored and striped) out of that box in replaced the two drives in the opensuse PC. As luck would have it, the motherboard can read the raid array.

    Now I'd like to clone (ghost) that win 7 array to one large disk so I have a bootable copy. Clonezilla can't handle the Nvida raid. Now I know that opensuse can handle Nvidia raid 10, even if whatever linux build clonezilla is on can't. (Yes, I tried the "magic" raid feature of clonezilla.)

    Now here comes the opensuse part of the question. If I load the 11.3 live CD on the win7 box, the opensuse software sees 4 drives rather than the raid array. If I could get the live opensuse CD to see one array, I assume I could DD the raid array onto the external hard drive.

    When I build the new win 7 PC, I'm going to set up raid 0 (mirror). I haven't tried this yet, but I assume I could copy the data to both sides of the mirrored array and the raid will be happy. If not, then just deleted one disk in the array and let raid build the mirror.

  2. #2
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    Default Re: live software raid

    Well at least at the moment OpenSuse and Linux in general does not like FAKE RAID (or BIOS assisted RAID). If you used true hardware RAID or software RAID it would be OK. But Windows does not like software RAID.

    RAID 0 is NOT mirror it is stripped. Every other sector goes to a different drive. If you lose 1 drive you lose all. RAID 1 is mirrored Where each sector is written to each drive.

  3. #3
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    Default Re: live software raid

    First off, I think that's pretty awesome if you're using raid 10 on a regular computer.

    Good on ya for setting that up in the first place. Although, when problems or changes need to be made, it sure is easier when you've setup the raid on dedicated card. But of course, its still cool to make use of what raid support is available on your motherboard.

    I can answer one of your questions though.

    When I build the new win 7 PC, I'm going to set up raid 0 (mirror). I haven't tried this yet, but I assume I could copy the data to both sides of the mirrored array and the raid will be happy. If not, then just deleted one disk in the array and let raid build the mirror.
    If you have a disk full of data and you pop in a blank disk next to it for the purpose of setting up raid 0 when you create the array it will wipe both disks.

    You have to build the array first from disks that you a aware the data will be wiped off of.

    Just making sure about that. Good luck.

  4. #4

    Default Re: live software raid

    The new PC will be mirrored. If the number is 1, so be it. [Could have sworn it was 0.] Anyway I was crazy to stripe it.

    The raid 10 is a function of the chipset and a software driver. I think that would be still be considered a fake raid or software raid, as opposed to using a raid card like a Promise.

    BTW, checking with Acronis, there is no way to clone the raid array to one external drive. The software does backup to an external drive using their proprietary format. I suppose that will have to do. That is, put two new drives in the new PC, set up the mirror array, then use acronis to restore the data.

    Raid 10 has worked in suse from at least version 10. When I built the PC, I tried a large number of distributions. The only distribution that handled the raid 10 array out of the box was opensuse. I have to assume it has whatever nvidia drivers are required are in the distribution.

  5. #5
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    Default Re: live software raid

    You might want to read this article

    RAID Reliability Issues

  6. #6

    Default Re: live software raid

    Now here comes the opensuse part of the question. If I load the 11.3 live CD on the win7 box, the opensuse software sees 4 drives rather than the raid array. If I could get the live opensuse CD to see one array, I assume I could DD the raid array onto the external hard drive.
    Hello,

    This should work! There is one little catch, the live cd does not start dmraid by default, which is why you see only the disks, not the array. You must start dmraid manually (something along the lines of dmraid -ay, but see the man page). If you are too lazy to read the man page (like someone I know very well), you can start the OpenSUSE installer and click through to the part where you create a custom partition setup and cancell the install ... and dmraid will have been started for you ... lol. It's almost certainly faster to read the man page ... but I have actually done this click through a few times ...

    oxala

  7. #7

    Default Re: live software raid

    I'm not above RTFMing. The thing is the opensuse install never required me to RTFM RAID.

    I read the PC Mag RAID document and learned about belly fat reduction too (pop under). I agree with it mostly and will only mirror. From what I have seen on my linux system with mirroring, you end up with two identical drives. The cloning software can find the data on the drives. If the array is healthy, cloning one drive is all you need.

    The comment about RAID being specific to the controller may or may not be true. I have seen other documents indicating that the manner in which data is placed on the drives is not proprietary to the controller. Within clonzilla is a mode where it tried to build the raid array in software as if the drives in the PC are completely independent. The problem is I can't make the mobo in this PC "unraid" the drives. I have used motherboards where this is possibly, that is you take a raid array and tell the bios it is no longer raid, thus showing individual drives. (The Gigabyte mobo would let me do this, but not Asus.)

    This thread in Tomshardware explains such a technique on how to read drivers that used to be part of a RAID array:
    Transfer RAID-0 Array? - NAS-RAID-Technologies - Storage

    I tried it without success using the ubuntu CD. [They have one CD that is both install and live.] I get the impression Clonzilla tries to do this as well.

  8. #8
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    Default Re: live software raid

    The comment about RAID being specific to the controller may or may not be true. I have seen other documents indicating that the manner in which data is placed on the drives is not proprietary to the controller.
    Disclaimer: I've little experience with the newer controllers and/or software RAID, but I have designed, built and set up many, many servers with hardware RAID (going all the way back to SCSI I on Adaptec ISA cards.)

    RAID controllers are idiosyncratic and temperamental little beasties. I've been told and have read many times that RAID is or is not specific to a given controller, but my experience is that there's no hard and fast rule. With some models the answer is definitely "Yes", with others "No" and with many it's a hit or miss proposition. Sometimes I can just replace the controller card with a similar one and the server works fine with no further attention. Other times (similar hardware), I have to rebuild the Array and restore the data from scratch.

    My point is this: RAID controllers obey the rules and work as the documents say they will most of the time but not always, so if you wonder if something will work or not the only way to be sure is to try it. Who knows, you might get lucky, but whatever you do be aware that you MUST have a separate backup of ALL your data FIRST. When you're dealing with any change to a RAID array there's no such thing as a change that won't endanger your data.
    MS user 1988-2008, Linux user 1998-present, openSUSE user since 2004
    (The first computer I used had a punch card reader)

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