>>> Lars Marowsky-Bree <[email protected]> schrieb am 22.04.2013 um 13:12 in >>> Nachricht <[email protected]>:
[...] > > Yes, I had complained about the massive logging of cLVM (which showed that > it's communication quite a lot (I'd say: way too much)), and the solution > being applied seems to be disabling logging. So the extensive communication > still happens. > > It *needs* to communicate this much for a concurrent activation. > > A first (and reasonably easy) step would be to introduce an LV-wide log > that would allow one node to fully own a cluster-mirrored LV > transparently, since most use cases do not actually perform concurrent > access. (Think Xen migration cases.) > > And only upconvert to the fully-fledged cluster mode once it is actually > opened for writing on multiple nodes. And then figure out some way to > speed that up further. Alas, that is not trivial to do. That's where OCFS2 comes in: When hosting Xen-VM images, multiple (we just use the trivial two-node cluster) hosts may acess one LV (i.e.: one filesystem), while access (if OCFS2 does allocate the data in big extents) to specific areas is mostly local to one node. I don't know how mirroring works at the moment, but I guess one node does the mirroring job for a whole LV. It would be probably better if the mirroring of one LV could be distributed among nodes so that each node would mirror the data it accesses. Then when idle, some task could do the rest (that is out of sync, if any). > > > > The CPU overhead will have improved some, but the basic design of cLVM2 > > > mirroring hasn't changed a lot. > > > > > > This is the same upstream and in all distributions, it is not SLES > > > specific. > > > > There were some rumours that Redhat's LVM is ahead of SUSE's by at least > one generation... > > At least not for released code, no, this is not the case. > ftp://sources.redhat.com/pub/lvm2/ - last release is from October. And > it doesn't improve this much at all. Specifically I meant "mirrorlog=mirrored" described for RHEL 6.1, vs. SLES': # lvcreate --mirrorlog mirrored -m 1 --name cLV1 -L 8G cVG Log type, "mirrored", is unavailable to cluster mirrors Of couse I couldn't check from the docs whether this would work for RHEL. Regards, Ulrich _______________________________________________ Linux-HA mailing list [email protected] http://lists.linux-ha.org/mailman/listinfo/linux-ha See also: http://linux-ha.org/ReportingProblems
