LVM2 - Crash

Hello,

I have a big problem with LVM2 (FC2) and the snapshot on a Dell PE1650 or Dell PE1750 (strangely not on a Dell GX240). The host is frozen after 3 snapshot.

A bug ??

------------
Essai FC2 sur PE1750
no raid
install + upgrade
/dev/sda1 38G 292M 36G 1% /
/dev/mapper/vg0-home 9.7G 33M 9.1G 1% /home
/dev/mapper/vg0-usr 5.8G 1.1G 4.5G 19% /usr
/dev/mapper/vg0-var 2.0G 206M 1.7G 11% /var
2.6.8-1.521smp
lvm2-2.00.15-2
[root@auto1 /]# lvscan
ACTIVE '/dev/vg0/home' [9.77 GB] next free (default)
ACTIVE '/dev/vg0/usr' [5.86 GB] next free (default)
ACTIVE '/dev/vg0/var' [1.95 GB] next free (default)
[root@auto1 /]# lvcreate -L500M -s -n snap1 /dev/vg0/var
Logical volume "snap1" created
commande : lvscan et lvdisplay, mount snap -> ok
Deuxiéme snapshot
[root@auto1 /]# lvscan
ACTIVE '/dev/vg0/home' [9.77 GB] next free (default)
ACTIVE '/dev/vg0/usr' [5.86 GB] next free (default)
ACTIVE Original '/dev/vg0/var' [1.95 GB] next free (default)
ACTIVE Snapshot '/dev/vg0/snap1' [500.00 MB] next free (default)
ACTIVE Snapshot '/dev/vg0/snap2' [500.00 MB] next free (default)
commande : lvscan et lvdisplay, mount snap -> ok
Troisiéme snapshot
[root@auto1 /]# lvscan
ACTIVE '/dev/vg0/home' [9.77 GB] next free (default)
ACTIVE '/dev/vg0/usr' [5.86 GB] next free (default)
ACTIVE Original '/dev/vg0/var' [1.95 GB] next free (default)
ACTIVE Snapshot '/dev/vg0/snap1' [500.00 MB] next free (default)
ACTIVE Snapshot '/dev/vg0/snap2' [500.00 MB] next free (default)
ACTIVE Snapshot '/dev/vg0/snap3' [500.00 MB] next free (default)
  freeze !!
no log, no message on the console, possibilité de commande tel que ls, df, ps j'essai de stopper le process lvscan -> impossible (état : D uninterruptible sleep (usually IO)) Try to remove snap : lvremove /dev/vg0/snapx -> freeze

Crash

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I'm seeing a lot of messages about snapshots sort of working... I should relay my experience here.

I did some testing with Snapshots in 2.6.8.1, and came up with variable results. Here's some stuff I found:

reiserfs works badly with read/write snapshots: writing to both the main filesystem and the snapshot hangs the filesystems permanently (even after writing stops), and stops LVM from being able to assign more snapshots/space/etc until a full reboot.

ext3 works OK, albeheit with a definite CPU hit. I tried low-level loads and it didn't crash, which was certainly better than with reiserfs.

I didn't try a whole lot of other filesystems though. Generally, it didn't seem quite stable enough, so I decided to wait a few iterations before working with it seriously. Does anyone know the status of work in this area? Or if there's some more patches waiting in -mm?

Cheers,
Liam

StrongBox Linux
http://www.strongboxlinux.com
"Making Security Friendly"