Hi, I try to add a bit memory management monitoring of services within the Xen resource, as I am usually interested in the services that the Xen resource provides and not whether Xen runs or not. I already got a lot of valuable feedback from Dejan, the state can be tracked here: http://developerbugs.linux-foundation.org/show_bug.cgi?id=1778
The problems right now are: 1) how to handle paused domU's 2) how to handle memory management The first is a bit work, but easy, before every action check in which condition the domU is, e.g. running/stopped/paused/... and then handle that situation accordingly. The second one is a bit trickier. Right now I have the Xen script working this way on startup/stop of the domU: 1. check how many memory is available 2. subtract the reserved memory for the dom0 3. check how many domains will after that action running, divide the result from step two with that number 4. set xm mem-set the memory for all virtual machines This is a very basic way to give all virtual machines more or less the same amount of memory. Nevertheless, in case more than one Xen resource is starting or stopping, this behavior is prone to race conditions, and I already have seen it failing. My workaround was to create orders, with symmetrical=no and score=0 for all Xen resources, so that only one can start at a time. Dejan suggested to add locking to the Xen resource script, but I fear that this will lead to new errors, e.g. assume the default-action-timeout=30s and you have 4 Xen resources, and all four will start up at the same time, then the first, will aquire the lock, the rest is waiting. Maybe everything will work for the second Xen resource too. But I assume then the startup of 3 and 4 will fail, because the default-action-timeout was hit. Is it possible serialize actions of a given type of resource? e.g. the Xen resource could be marked as serialization needed, that means, in case there are multiple Xen resources in a cluster, actions to these resources are not allowed to happen at the same time? So that not the Xen resource script would be responsible for locking and allowing/disallowing actions to itself, but the CRMD is responsible. This could be made more fine-grained, in case you say, it is not allowed to have action for resource Xen at the same time on the same node, but it is allowed to have multiple actions to the Xen resource in the cluster. Then the LRMD could be made responsible to serialize the actions. Does that makes sense to anyone, or maybe is that already possible? kind regards Sebastian _______________________________________________________ Linux-HA-Dev: [email protected] http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev Home Page: http://linux-ha.org/
