[CentOS] hard drive failing in linux raid
alfrare at e-alinux.com
Wed Nov 8 01:51:02 UTC 2006
I tested RAID 1 with differents size hard disk , it is work.
You need first, execute command sfdisk -l /dev/hd_GOOD > partitions.txt
Second execute command sfdisk /dev/hd_NEWDISK < partitons.txt.
After recover process normal RAID recover.
I hope to help you
Aleksandar Milivojevic wrote:
> Joseph Cheng wrote:
>> Hello all. I have a server with a linux software raid1 setup between
>> two drives of the same model....one hard drive as primary ide master
>> and second hard drive as secondary master. Now primary master hard
>> drive is displaying a lot of SMART errors so I would like to remove it
>> and replace with another drive....different brand but same size.
>> Partitions are /dev/md0 till /dev/md5. I think I know what to do based
>> on mdadm man page and this list's archives but there is no harm in
>> confirming right? ;) From this post
>> http://lists.centos.org/pipermail/centos/2006-April/063076.html I plan
>> on removing the old partitions from the array like this..... mdadm
>> /dev/mdx -r /dev/hdax. Then I will shut down the server, replace the
>> hard drive, make the server boot from second IDE drive and hopefully
>> boot into Centos. From there do I have to manually create each
>> /dev/mdx partition and then re-add them like this....mdadm /dev/mdx -a
>> /dev/hdax ? That is what I am not sure about whether I have to
>> partiton the drive exactly like the old one or if Centos mdadm can do
>> some magic for me with a blank drive. TIA!!
> Couple of things to watch out.
> What boot loader are you using? If it is Grub, check if it was
> installed on partition, not in MBR of first drive. If it was in MBR,
> there is a good chance you don't have it mirrored on second drive.
> You'll need working boot loader (most likely Grub) on second drive in
> order to boot from it.
> Disk size... It is next to impossible to find "different brand but same
> size". If the label says 80GB, it means "somewhere around 80GB". You
> want to look at LBA count (it's printed almost on all hard drives, but
> often hard to find in specifications). It's basically the number of
> sectors that the drive has. You want the drive that has at least the
> number of sectors as your existing drive(s). If you already got the new
> drive and it is few sectors short, all is not lost. You'll just have a
> bit of additional work. You'll need to shrink some partition. Swap
> partition is usually good candidate since it doesn't contain any data.
> You can also shrink a partition that holds file system, but if you make
> mistake you might end up loosing some data. Another thing to keep in
> mind when shrinking partitions is that Linux stores RAID metadata at the
> end of the partition. If you are shrinking partition that holds Linux
> RAID device, the best thing (if it was RAID 1 volume) is to ditch the md
> device for it, shrink the file system to smaller size, and recreate md
> device. Your data should survive the operation. When shrinking file
> system, have in mind you'll need to have some extra space of RAID
> metadata information at the end of partition (you'll need to shrink file
> system to be smaller than the final partition size).
> You'll need to partition the new drive manually. Remember to tag
> partitions as "Linux raid autodetect" (by default fdisk will tag them as
> "Linux"). Tag for Linux raid autodetect is fd. New partitions must be
> the same size (in blocks) as the partitions you are replacing or larger.
> If you make them larger, the extra space will be unused.
> If your boot loader was installed in the partition, it'll get mirrored
> automatically. If it was in MBR, you'll have to install it by hand onto
> the drive you just replaced.
> The rest should more or less go smooth.
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