[CentOS] Boot from degraded sw RAID 1

Fajar Priyanto fajarpri at cbn.net.id
Thu Aug 14 00:38:02 UTC 2008


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Eduardo Grosclaude wrote:
> 1. Build a 100MB RAID-type partition on each disk
> 2. Build a second RAID-type partition taking the remaining space on each disk
> 3. Build a RAID 1 device over the small partitions
> 4. Build a second RAID 1 device over the bigger ones
> 5. Declare /boot as ext3 to live on the smaller RAID 1 device
> 6. Declare an LVM PV to live on the bigger one
> 7. Build a VG on the PV, then build LVs for swap, / and /data on the VG
> 
> Only problem is, I numbly have failed to follow [1] in that I left
> Disk Druid to make partitions wherever it chooses, so now I have
> cross-named partitions... md0 is the bigger RAID 1 device with
> /dev/sda2 AND /dev/sdb1... and md1 is the smaller one with /dev/sda1
> AND /dev/sdb2. Oh well, things can't get complicated on this, I tell
> myself.

To prevent the mix-up of partitions sequence during installation, here's
what I do (sorry for the copy paste :))
1. Build a 100MB RAID-type partition on each disk
3. Build a RAID 1 device over the small partitions
2. Build a second RAID-type partition taking the remaining space on each
disk
4. Build a second RAID 1 device over the bigger ones

That way /dev/{sda1,sdb1} will surely be /dev/md0, and /dev/{sda2,sdb2}
will be /dev/md1.

To address the second issue of grub is not installed on the second RAID1
disk, I thought it was an old bug in Centos4.0 which since then has been
fixed. I'm not sure if it's related, but as a workaround you can try
labeling the raid array so that it wont matter if the computer
recognizes it as sda or sdb. Here's a good article:
http://cgerada.blogspot.com/2008/07/software-raid-on-linux.html

HTH,
- --
Fajar Priyanto | Reg'd Linux User #327841 | Linux tutorial
http://linux2.arinet.org
13:10:54 up 5:02, 2.6.24-18-generic GNU/Linux
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