[DRBD-user] automated LVM snapshots: interfere with nested LVM configuration

Lars Ellenberg lars.ellenberg at linbit.com
Fri Apr 11 22:37:07 CEST 2014

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On Fri, Apr 11, 2014 at 10:14:50PM +0200, Bart Coninckx wrote:
> 	Hi all,
> when enabling automated LVM snapshots, do they interfere (or vice
> versa) with the LVM configurations of a nested LVM setup?

I think you need to elaborate a bit more...

What would your "nested LVM setup" look like,
and where/how would you do the "automated" snapshots?

I've seen problems with LVM,
if you snapshot the LV below DRBD
(which temporarily has to suspend that LV)
while having the DRBD "visible" to the LVM tools
(not filtered out in the device filter of lvm.conf)...

The tools could end up scanning the DRBD for LVM meta data,
while having the lower LV suspended, which will obviously cause those
tools to deadlock (and DRBD to remain "hung" or blocked as well).

If you really need a nested LVM setup
where both "layers" are visible to the host
(not in the sense of LV -> DRBD -> virtual machine image,
 and then LVM inside that VM)

I'd recommend to utilize the "LVM_SYSTEM_DIR" environment variable,
and have two (or more) separate lvm.conf with suitable filter settings,
with the "outer" one being the default (and filter out all DRBD),
and any "inner" one(s) only being used explicitly by setting the
respective LVM_SYSTEM_DIR (and filter out everything BUT the
corresponding DRBD).


: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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