[Techtalk] brainstorming lvm + xfs + nfs

[Kristina Clair]

Hi All,

I have an interesting problem which I've been brainstorming about, and
I thought maybe some of you might have some creative ideas... ;-)

We're setting up a fileserver which is an lvm2 1TB device (hardware
raid 5) with xfs.  This filesystem will be mounted by a cluster of
webservers and will store all the docroots.  We need to provide daily
snapshots, which lvm can do, and which works wonderfully if the
filesystem isn't in use.  However, once the filesystem is mounted on
the webservers for an extended period of time (a day, for example),
lvcreate (which makes the snapshots) hangs when it is trying to
suspend the filesystem.  So my theory is that if apache is using the
filesystem, lvm is unable to suspend it.

One idea was to use xfs_freeze before lvcreate and then somehow tell
lvcreate to not worry about suspending the filesystem, but I don't
think this is possible.  At least that is the impression I got from
the lvm list.

Having the filesystem unmounted for any period of time is really not
an option.   Someone suggested trying to remount the filesystem
temporarily as read-only on the webservers, which I will try, but even
that is not ideal.

I can't really see past these few solutions.  Does anyone see it from
a different perspective?

Thanks!
Kristina