On Tue, 13 Apr 2010, Bernhard Gschaider wrote:
xfs_db -r /dev/mapper/VolGroup00-LogVol04
xfs_db: unexpected XFS SB magic number 0x00000000
xfs_db: read failed: Invalid argument
xfs_db: data size check failed
cache_node_purge: refcount was 1, not zero (node=0x2a25c20)
xfs_db: cannot read root inode (22)
Hi Bernhard. Hmm that doesn't sound good.
The file-system is still mounted and working and I don't dare to do
anything about it (am in a mild state of panic) because I think it
might not come back if I do.
I think your choice to sit back and evaluate your options before acting is
a wise one, especially since the filesystem is apparently mounted and
Depending on how worried you are there are various options available. Eg
you could declare an emergency on the server and use xfs_freeze to freeze
the filesystem while you take a backup. Note - I have never used
xfs_freeze like this, it is just a suggestion. Naturally this will cause
an outage and problems for users.
Alternatively you could use xfsdump to capture an incremental or full
backup on the running system. (depending on whether you already have a
level 0 xfs dump file or not). The developers have confirmed (on this
list) that xfsdump will provide a consistent backup on a live filesystem.
Please note that any heavy I/O (like a backup) has the potential to cause
problems on a sick filesystem. In my experience xfs is inclined to
automatically remount read-only if it detects problems. While this can be
catastrophic for running processes it is helpful in protecting data so I'm
happy it works this way.
One last note. I hope you have good backups already. If you don't then
this is the time to start taking good backups.
These are the notes from my backup talk:
I swear to god: I did not do anything else with the xfs_*-commands
than the stuff mentioned above
I defrag XFS filesystems from cron as recommended by SGI and I've never
had a problem. Maybe defragmentation didn't cause the problem - maybe it
just revealed an underlying problem.
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