Hi list,
in my endless search for information :) I was testing DRBD in dual
primary mode + GFS2. The goal is "the same": running a replicated,
2-node KVM setup where disk images are located on the GFS2 filesystem.
I know how to integrate DRBD with corosync/pacemaker, but I wonder how
the system will perform under load. More specifically, it is my
understanding that GFS2 inevitably has some significan overhead compared
to a traditional, one-node filesystem, and this can lead to decreased
performance.
This should be especially true when restarting (or live-migrate) a
virtual machine on the other host: as the first node has cached
significan portion of the vm disk, GFS2 will, on every first read on the
new host, fire its coherency protocol to be sure to update the first's
node in-memory cached data. The overhead should be lowered by not using
cache at all (ie: cache=none, which implies O_DIRECT), but this will
also case degraded peformance in the common case (ie: when all is
working correctly and VMs run on the first node only).
So I ask: has some of you direct experience with a similar setup? How do
you feel about? Any other suggestions?
Thanks.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: [email protected] - [email protected]
GPG public key ID: FF5F32A8
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