----- On Jun 7, 2016, at 3:53 PM, Ferenc Wágner [email protected] wrote:
> "Lentes, Bernd" <[email protected]> writes: > >> Ok. Does DLM takes care that a LV just can be used on one host ? > > No. Even plain LVM uses locks to serialize access to its metadata > (avoid concurrent writes corrupting it). These locks are provided by > the host kernel (locking_type=1). DLM extends the locking concept to a > full cluster from a single host, which is exactly what cLVM needs. This > is activated by locking_type=3. So DLM and cLVM just takes care that the metadata is consistent. None of them controls any access to the LV itself ? > >> cLVM just takes care that the naming is the same on all nodes, right? > > More than that. As above, it keeps the LVM metadata consistent amongst > the members of the cluster. It can also activate LVs on all members > ("global" activation), or ensure that an LV is active on a single member > only ("exclusive" activation). > >>>> Later on it's possible that some vm's run on host 1 and some on host 2. >>>> Does >>>> clvm needs to be a ressource managed by the cluster manager? > > The clvm daemon can be handled as a cloned cluster resource, but it > isn't necessary. It requires corosync (or some other membership/ > communication layer) and DLM to work. DLM can be configured to do its > own fencing or to use that of Pacemaker (if present). > >>>> If i use a fs inside the lv, a "normal" fs like ext3 is sufficient, i >>>> think. But >>>> it has to be a cluster ressource, right ? > > If your filesystem is a plain cluster resource, then your resource > manager will ensure that it isn't mounted on more than one node, and > everything should be all right. > > Same with VMs on LVs: assuming no LV is used by two VMs (which would > bring back the previous problem on another level) and your VMs are > non-clone cluster resources, your resource manager will ensure that each > LV is used by a single VM only (on whichever host), and everything > should be all right, even though your LVs are active on all hosts (which > makes live migration possible, if your resource agent supports that). > -- Does the LV need to be a ressource (if i don't have a FS) ? From what i understand from what you say the LV's are active on all hosts, and the ressource manager controls that a VM is just running on one host, so the LV is just used by one host. Right ? So it has not to be a ressource. Bernd Helmholtz Zentrum Muenchen Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH) Ingolstaedter Landstr. 1 85764 Neuherberg www.helmholtz-muenchen.de Aufsichtsratsvorsitzende: MinDir'in Baerbel Brumme-Bothe Geschaeftsfuehrer: Prof. Dr. Guenther Wess, Dr. Alfons Enhsen, Renate Schlusen (komm.) Registergericht: Amtsgericht Muenchen HRB 6466 USt-IdNr: DE 129521671 _______________________________________________ Users mailing list: [email protected] http://clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
