On 23/08/2013, at 5:15 PM, Ulrich Windl <[email protected]> wrote:
>>>> Andrew Beekhof <[email protected]> schrieb am 23.08.2013 um 02:14 in >>>> Nachricht > <[email protected]>: > >> 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? > > As it turned out: "not yet" ;-) It only works for explicit "ordering". That makes more sense. > > >> If so, crmsh must be re-writing this into something other than a group. > > This should not be much of a problem; the problem seems to be: How to convert > such structures back to the original notation? Quite hard to know what the original form was > >> >>> (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. > > I know, and the PDP-8 had 128kB RAM. But things can change. Not groups of groups. Hell, I'd get rid of groups completely if I could > >> >>> 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 > > > > _______________________________________________ > 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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