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

[Les Mikesell]

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