--- Les Mikesell lesmikesell@gmail.com wrote:
On Wed, 2005-04-27 at 10:44, Aleksandar Milivojevic wrote:
You'd need to resize file systems after you import
partitions into MD.
An e2fsck/resize2fs would take care of that. Do an
"fsck -f /dev/md0"
(for example). It will complain that information in
superblock is wrong
(partition size fsck sees is smaller than what it found
in superblock).
Just answer "no" to abort question. After you did
fsck, you need to
do "resize2fs /dev/md0". Repeat for all md devices you
created.
For above, the file systems should be either unmounted,
or mounted read
only. The best thing to do is to boot from CD into
rescue mode, and do
all job from it.
The reason is that MD uses couple of last blocks for
metadata
information, and that space is no longer usable for
file system data.
So your /dev/md* metadisks will be slightly smaller
than partitions you
created them on.
What happens if existing files are on these blocks before you convert?
When you are creating mirrors, make sure you list
devices in right
order. Data is always copied from first disk you
specify to second
disk. If you get them the wrong way around, you loose
data.
Another approach that might be safer is to create a 'broken' mirror first by specifying the 2nd device as 'missing'. Then you can build a filesystem on the md device and mount it somewhere and copy the files over from the existing partition. Then unmount the old partition, remount the raid device in its place (adjusting /etc/fstab to match) and use mdadm to add the old partition into the new raid, which will hot-sync it to match the new setup.
Good idea, I will give this a try this evening. Thanks for your input concerning this issue.
There are some rather good HOWTOs on this question
(with much longer,
detailed and better descriptions of migration process).
Use the Google
Luke.
I looked for this and found lots of info on building RAIDs but none about preserving an existing filesystem while converting to a mirror. Can you provide a link or a good search term to pick that up? Also, I have noticed that after syncing the mirrored drives, you can split them and mount a single drive from it into another machine without making an md device first. (For example, if one part is on a USB/firewire drive, you can plug it into a different machine and mount the /dev/sda? partition it becomes.) However, I don't know if this is harmful or not. Does anyone know if, after running a while in this mode it will still work correctly if detected as an md? device (with or without resyncing to a partner)?
-- Les Mikesell les@futuresource.com
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