[root]
> Hi,
Hello.
> I've created mirrored striped arrays (Raid10) and am not confident that
> my first striped set is in fact being mirrored on my second striped set.
First question: did you make backups? :)
> When the mirrored mdX devices are created, cat /proc/mdstat does show
> that re-synching is taking place. However, if I mount an mdX that is
> part of my second striped set, I see NO files, just a lost+found
> directory. Hmm, I didn't mount as read-only. It this significant?
Any chance we could see your /proc/mdstat output?
> What techniques can I use to verify that the second striped set is being
> mirrored? Is there a raidtool to force resynching?
mkraid'ing md10-14 will need to write to the ends of md0-9, possibly
corrupting the filesystems already in place (with the blessed data
being on md0-4, it would appear).
Although it's not broken out as a separate section, the method for getting
a mirror made of already in-place data isn't extremely nice, but it has
been effective for many in the past. It's covered as "Method 2" at:
http://www.linuxdoc.org/HOWTO/Software-RAID-HOWTO-4.html#ss4.12
If you have an ext2 resizer that you trust to shrink the fs enough for
the raid superblock, you can try that and avoid the step of copying over
data manually. Not recommended, of course, but it's a possibility.
> If, perchance, an mdX on the first-striped set has a problem, will the
> mirrored device kick in and re-synch the striped mdX with the problem?
> When this happens (as I'm sure it probably will at some point), how will
> I know that it is occurring? I am guessing that the first striped set
> will be out of operation until it is repaired by re-synching with the
> mirrored set.
>
> How can mirroring be effectively used & monitored?
The major problem here is that once you create (via the failed-disk method)
the raid10, you *need* to start mounting the md10-14 devices. Manually
dealing with the underlying md0-9 devices isn't supported after that point.
It boils down to the fact that raid1 is "write to md10, mirror the
writes across md0 and md5" and not "the raid1 module should catch all
writes to md0 and automatically mirror them to md5". You have to use the
raid1 mdX device you created or you best-case lose raid1 functionality,
worst-case lose data.
> fstab file:
>
> /dev/md1 /local ext2 defaults 1 2
> /dev/md0 /opt ext2 defaults 1 2
> /dev/md4 /tmp ext2 defaults 1 2
> /dev/md2 /usr ext2 defaults 1 2
> /dev/md3 /var ext2 defaults 1 2
After the "method 2" (failed-disk) steps to get the mirrored/striped
raid10's up and running, you'll need to change these by "adding 10" to
each (md11, md10, md14, md12, md13) so you're using the raid10 devices
and not an underlying raid0 device.
HTH, HAND
James
--
James Manning <[EMAIL PROTECTED]>
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