DRBD/LVM, LVM/DRBD, LVM/DRBD/LVM, LVM/DRBD/DRBD/LVM (3 nodes) should all
work.
With DRBD over LVM, you gain the ability to make an automatic snapshot
of the last consistent state of a resource before you start synchronizing.
Make sure you use the latest DRBD and a recent kernel. If you can't, do
read all the release notes carefully to work around known critical bugs.
Forget about barriers. They don't even exist anymore in recent kernels
- DRBD was updated recently to match that.
Barriers, flushes, syncs etc. only mitigate the fact that your caches
are unsafe. Do yourself a favor: use safe caches (BBU, PSU) and live a
simple life.
We've been doing LVM over DRBD over LVM over HW RAID+WiMax in production
for 2 years and it works: one building was destroyed in a fire and there
was no data loss and no server downtime the fsck we forced (that didn't
find errors).
Our cluster is not fast. We don't know if that's because of DRBD because
our stack is complicated. It's still usually fast enough for our use.
Lionel Sausin
Le 08/11/2012 15:33, Denis Cardon a écrit :
it does work :-)
I'm not at all sure what's better performance-wise.
If your backing device is an LV, you do incur a write penalty to all
drbd interactions on both nodes.
Still, that doesn't mean that the setup will be slower than the other
way around.
It's usually a good idea to make your own tests, hopefully with a most
befitting workload.
I've been digging into this issue recently. There is some drbd
documentation with this scenario
(http://www.drbd.org/users-guide/s-lvm-lv-as-drbd-backing-dev.html),
and I have done such setup in the past. It does work, but I was
wondering if it is safe?
DRBD by default make use of barrier (unless no-disk-barrier is set
with a BBU RAID backend), and such barrier where not correctly
implemented in LVM before kernel 2.6.33. So I guess there are some
cases where there is problems, eg. with software MD raid.
Cheers,
Denis
Cheers,
Felix
_______________________________________________
drbd-user mailing list
[email protected]
http://lists.linbit.com/mailman/listinfo/drbd-user
_______________________________________________
drbd-user mailing list
[email protected]
http://lists.linbit.com/mailman/listinfo/drbd-user
