[CentOS] FSCK on mounted filesystem (LVM/DRBD)?

Hi All.

I have two running servers (drbd primary, drbd secondary). When there is a
problem with one of them we switch to the second one. Currently on the
/dev/drbd0 (it has /xxx ext3 filesystem directly on it) we have some
filesystem problems (after fsck -n). I would like to correct these errors
but the filesystem should be unmounted first (I would like to avoid it if
possible).

Is there a way to make fsck -a on mounted filesystem for ext3? My setup is:

ext3 filesystem (problems)
^
DRBD
^
LVS
^
RAID

Any ideas?

Best regards,
Rafal.