[CentOS] preferred software RAID 10?

Linux linuxlist at gmail.com
Fri Jul 18 14:17:24 UTC 2008

On Fri, Jul 18, 2008 at 4:15 AM, David Mackintosh
<David.Mackintosh at xdroop.com> wrote:
> To get back to the OP: I've done a RAID-10 under CentOS, and the
> problem I encountered was that the kernel wasn't smart enough to
> assemble the RAID without a properly populated /etc/mdadm.conf file.

Well, I have many working configurations with 4 disk cheap machines.
Guess I should say something.

/sd[abcd]1: 20 GB, ext3, RAID-1 as /dev/md0, linux-raid autodetect
(type: fd), boot flag active, mounted as "/" (incl. /boot)
/sd[abcd][23...]: whatever you want

I installed grub like this:

grub> device (hd0) /dev/sda  [repeat these 3 steps for all disks respectively]
grub> root (hd0,0)
grub> setup (hd0)

And this is from my grub.conf

"kernel /boot/2.6...../bzImage root=/dev/md0"

Kernel updates etc does not cause any problems. I only update
grub.conf and bzImage file and reboot.

You should compile raid-related stuff in kernel directly (not modules)
and set raid partitions to "fd", this way, you do not need any
mdadm.conf or related stuff.

I had many recovery nightmares. Once, one system survived with "sdc"
only because of electricity. It seems no use but I had a chance to
change failed disks, rebuild my unrecoverable raid10 which was on
second part and restore backups without reinstalling operating system.
It depends on mainboard, SATA controller and may be disks but usually
modern hardware recovers hard errors and somehow continues with
working disks despite some bus-speed penalty.

If I missed something and repeated meaningless facts, sorry for being
lazy to read the thread from beginning...


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