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On Monday 20 February 2006 09:57, "Nick Smith" <nick.smith79@×××××.com> |
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wrote about '[gentoo-user] raid/partition question': |
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> just wanted to ask before i mess something up. |
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> i have booted off the install cd, created a raidtab with my mirrored |
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> drives on it. i have created the raid. now, do i go in and setup the |
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> partitions i want on that raid? or should i have done that before |
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> creating the raid? so instead of having one big mirror and then |
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> partitioning that, do i need to create my seperate partitions and then |
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> mark them as "fd" and then create each raid seperate? |
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I would suggest partitioning the drives identically, then using mdadm to |
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create your raid devices. The reason I say this is because the kernel |
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does not seem to have any room in the device node space for partitions on |
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an md device. |
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I could be wrong here; but I know partition and then build will work. |
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If you'll look at the major/minor number of IDE devices, you'll see that |
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hda and hdb have the same major, but the minor number on hdb is +64... |
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thus this allows 63 recognized partitions / disk labels on an IDE device. |
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(hda1 is +1 minor from hda, hda2 is +2, etc.; similarly for hdb) |
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If you do the same investigation on SCSI/SATA devices, you'll see that sda |
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and sdb have the same major number, but the minor number on sdb is +16... |
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thus only 15 partitions / disk labels are recognized on a SCSI/SATA |
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device. I do believe we recently had a member of gentoo-user run into |
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this problem. (Switching to not using partitions as much will help; I |
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prefer LVM LVs myself.) |
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Finally, you can look at the software raid devices, you'll see that md0 and |
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md1 have the same major number (9) and the minor number on md1 (1) is only |
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+1 from the minor number on md0 (0). Due do this, I fear that the kernel |
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may not properly recognize partitions / disk labels on software raid |
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devices. |
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It's entirely possible that partitions on software raid devices use a |
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different major number and/or use dynamic minor numbers so partitioning |
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the raid device may work -- I just can't recommend it because I don't know |
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it'll work and I know partitioning first, then raid-ing the partitions |
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does work. |
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As the other poster said, be careful with how you treat your bootable |
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partition. It must be a partition recognized by your bootloader, on a |
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disk recognized by the BIOS / EMI, using a filesystem understood by your |
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bootloader. If you use the old-style software raid (no superblock; by |
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default mdadm does create a superblock), you can use raid 1 for boot, but |
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each component partition should satisfy all the conditions for a bootable |
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partition. |
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-- |
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Boyd Stephen Smith Jr. |
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bss03@××××××××××.com |
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ICQ: 514984 YM/AIM: DaTwinkDaddy |
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-- |
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gentoo-user@g.o mailing list |
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