Op 4/22/2013 3:18 PM, Ulrich Windl schreef: >>>> 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 Hi Ulrich.
Little surprised. You have been informed that with SLES11SP3 (HAE), "lvcreate --mirrorlog mirrored"" will be available. Michael _______________________________________________ Linux-HA mailing list [email protected] http://lists.linux-ha.org/mailman/listinfo/linux-ha See also: http://linux-ha.org/ReportingProblems
