[CentOS] Turn an ext2 filesystem into a component of a mirrored RAID?

Les Mikesell lesmikesell at gmail.com
Tue Nov 28 04:13:11 UTC 2006

On 11/27/06, Bart Schaefer <barton.schaefer at gmail.com> wrote:

> > If you can be down a few hours, you should be able to boot the
> > install CD in rescue mode and
> > dd bs=1M if=/dev/hda of=/dev/hdb (being very careful that those
> > are the correct devices for the source and target respectively).
> > I'd expect that to take about 3 hours to complete, depending on
> > your drives and controller.
> That may be what we have to try.  This isn't the root filesystem, so
> we should just be able to unmount it during the dd and not have to
> reboot?

Yes, you just have to be sure nothing changes during the copy and
unmounting will take care of that.

> > Another approach
> > would be to put the drive directly in the 2nd server and do the
> > rsync over the network.  This would probably complete over a weekend.
> The second server is 2900 miles away in another data center with no
> dedicated network between the locations, so this probably isn't going
> to work ...

You could use some other local machine.

> > If the files are changing, you can do one run with the machine active,
> > then repeat it when no changes are happening.  The 2nd run should go
> > very quickly since it only has to copy the differences.
> Unfortunately we're talking about a relatively small number of
> relatively huge files, so the checksumming is a significant portion of
> the rsync time.

If you don't use the -i option, rsync will skip over existing files that match
in length and timestamps without doing the block checksum compares.
Of course if the big files are changing, this won't help much.

  Les Mikesell
   lesmikesell at gmail.com

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