On 04/11/2011 13:53, Alex wrote:
Hi,
I have a fedora15 system with two 80GB SATA disks using RAID1
[...]
I believe the boot sector is installed on sda, which is also the bad
disk. If I remove the disk to replace it, I'm concerned the system
will no longer boot.
Can you point me to instructions on the best way to replace a disk?
If you used Fedora's installer to set up the md RAIDs in the first
place, you will be able to boot off the second drive, as the Fedora
installer will have installed grub on it as well. You would have to tell
your BIOS to boot from it though.
If you've room in the case and spare SATA ports for a third drive (with
which to replace the failing drive), put it in and assuming it appears
as sdc I'd do the switcheroo by growing the array to three drives then
shrinking it again, something like this (all off the top of my head, so
check it first by looking at the man page, which will help you
understand what's going on anyway):
# sfdisk -d /dev/sda
Note down where sda1 starts. It will likely be either 63 or 2048.
# dd if=/dev/sda of=/dev/sdc bs=512 count=<howevermanyitwas>
This will copy the partition table and boot code.
# blockdev --rereadpt /dev/sdc
# mdadm /dev/md0 --add /dev/sdc1
# mdadm /dev/md1 --add /dev/sdc2
# mdadm --grow /dev/md0 -n3
# mdadm --grow /dev/md1 -n3
Wait for this to finish, either by looking at /proc/mdstat from time to
time, or using mdadm --wait /dev/md1. This gives you a three-way mirror.
It's possible this process will cause sda to fail, but that's OK. Next
we want to remove the duff drive:
# mdadm /dev/md0 --fail /dev/sda1 --remove /dev/sda1
# mdadm /dev/md1 --fail /dev/sda2 --remove /dev/sda2
# mdadm --grow /dev/md0 -n2
# mdadm --grow /dev/md1 -n2
Now you can shut down again, and install the new drive in the place of
the original failing drive.
Cheers,
John.
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