Thank you all for the answers so far. The main problem with the raid
is that the partition table has been overwritten. I don't know how it
happened but it seems that another machine could see the raid device
during a kickstart installation and used it (some of our kickstart
files use the clearpart --all --initlabel option).
However I was able to recover a partition table with gpart (tried
TestDisk befor and didn't work) and will now see if I can somehow
recover the MGS and MDTs.
Regards
Tom
Am 15.07.2009 um 15:53 schrieb Andreas Dilger:
On Jul 15, 2009 08:32 -0400, Brian J. Murrell wrote:
Even if it was completely wiped, the process of scanning the entire
disk
looking for "signatures" that can help identify a likely partition
beginning and then recreate the partition table is usually quite
successful. You might want to look into the "gpart" tool for this.
On Wed, 2009-07-15 at 10:53 +0200, Tom Woezel wrote:
Now here is my question is, it possible to create a new MGS and new
MDTs and somehow connect the old OSTs to them?
No. There is nothing on the OSTs that indicate what file an object
belongs to. This is why we are adamant about MDT storage being
reliable
and backed up.
That isn't totally correct - there is an xattr on each OST object that
contains the MDT inode number and stripe index for that object. That
doesn't help much in this case, because you will still have a whole
filesystem of objects without filenames.
Without knowing the whole story of your MDT/RAID saga, I'd say
gpart is
your best bet.
Recovering the MDS data using gpart seems like a better idea. If the
corruption is in the RAID layout itself, that is a harder issue to
fix.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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