On 22/08/2013, at 7:31 PM, Ulrich Windl <[email protected]> wrote:
> Hi! > > Suppose you have an application A that needs two filesystems F1 and F2. The > filesystems are on separate LVM VGs VG1 and VG2 with LVs L1 and L2, > respectively. The RAID R1 and R2 provide the LVM PVs. > > (Actually we have one group that has 58 primitives in them with both > dimensions being wider than in this example) > > So you can configure > "group grp_A R1 R2 VG1 VG2 F1 F2 A" (assuming the elements are primitives > already configured) > > Now for example if R2 has a problem, the cluster will restart the whole group > of resources, even that sequence that is unaffected (R1 VG1 F1). This causes > extra operations and time for recovery what you don't like. So don't put them in a group? > > What you can do now is having parallel execution like this > "group grp_A (R1 R2) (VG1 VG2) (F1 F2) A" You're saying this is currently possible? If so, crmsh must be re-writing this into something other than a group. > (Note that this is probably a bad idea as the RAIDs and VGs (and maybe mount > also) most likely use a common lock each that forces serialization) > > For the same failure scenario R2 wouldn't be restarted, so the gain is small. > A better approach seems to be > "group grp_A (R1 VG1 F1) (R2 VG2 F2) A" > > Now for the same failure R1, VG1, and F1 will survive; unfortunately if R1 > fails, then everything will be restarted, like in the beginning. > > So what you really want is > "group grp_A ((R1 VG1 F1) (R2 VG2 F2)) A" > > Now if R2 fails, then R1, VG1, and F1 will survive, and if R1 fails, then R2, > VG2 and F2 will survive > > Unfortunately the syntax of the last example is not supported. I'm surprised the one before it is even supported. Groups of groups have never been supported. > This one isn't either: > > group grp_1 R1 VG1 F1 > group grp_2 R2 VG2 F2 > group grp_A (grp_1 grp_2) A > > So a group of groups would be nice to have. I thought about that long time > ago, but only yesterday I learned about the syntax of "netgroups" which has > exactly that: a netgroup can contain another netgroup ;-) > > Regards, > Ulrich > > > _______________________________________________ > Linux-HA mailing list > [email protected] > http://lists.linux-ha.org/mailman/listinfo/linux-ha > See also: http://linux-ha.org/ReportingProblems
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