Digimer wrote: > > On 11/22/2011 02:22 PM, Lentes, Bernd wrote: > > Hi, > > > > i have a bit experience in LVM, but not in cLVM. So i have > some principal questions: > > My idea is to establish a HA-Cluster with two nodes. The > ressources which are managed by the cluster are virtual > machines (KVM). > > I have a FC SAN, where the vm's will reside. I want to > create vdisks in my SAN which are integrated as a PV in both > hosts. On top of the PV's i will create a VG, and finally > LV's. For each VM one LV. > > > > How are things going with cLVM ? Do i have to create PV ==> > VG ==> LV seperately ? Or does cLVM replicate the > information from one host to the other ? So that i have to > create PV, VG and LV only once on the first node and this > configuration is replicated to the second host. > > > > What is about e.g. resizing a LV ? Is this replicated, or > do i have to resize twice, on each host ? > > > > E.g. one host is running VM3 in the corresponding lv3 on > the first host. Is the second host able to access lv3 > simultaneously or is there a kind of locking ? > > > > Is it possible to run some vm's on the first host and > others on the second (as a kind of load-balancing) ? > > > > Is it possible to perform a live-migration from one host to > the other in this scenario ? > > > > I will not install a filesystem in the lv's, because i got > recommendations to run the vm's in bare partitions, this > would be faster. > > > > > > Thanks for any eye-opening answer. > > > > > > Bernd > > Clustered LVM is, effectively, just normal LVM with external > (clustered) > locking using DLM. Once built, anything you do on one node > will be seen > immediately on all other nodes. > > Mount your iSCSI target as your normally would on all nodes. On one > node, with clvmd running, 'pvcreate /dev/foo' then 'vgcreate > -c y -n bar > /dev/foo'. If you then run 'vgscan' on all other nodes, > you'll see the > VG you just created. > > Be absolutely sure you configure fencing in your cluster! If a node > falls silent, it must be forcibly removed from the cluster before any > recovery can commence. Failed fencing will hang the cluster, and > short-circuited fencing will lead to corruption. > > Finally, yes, you can do live migration between nodes in the same > cluster (specifically, they need to be in the same DLM lockspace). > > I use clvmd quite a bit, feel free to ask if you have any more > questions. I also have an in-progress tutorial using clvmd on > DRBD, but > you could just replace "/dev/drbdX" with the appropriate iSCSI target > and the rest is the same. > > -- Hi Digimer, we met already on the DRBD-ML. clvmd must be running on all nodes ? I'm planning to implement fencing. I use two HP Server which support iLO. Using this i can restart a server when the OS is not longer accessible. I think that's a kind of STONITH. Is that what you describe with "short-circuited fencing" ? You recommend not using a STONITH method ? What else can i use for fencing ? What is about concurrent access from both nodes to the same lv ? Is that possible with cLVM ? Does cLVM sync access from the two nodes, or does it lock the lv so that only one has exclusive access to the lv ? Thanks for your answer. Bernd Helmholtz Zentrum München Deutsches Forschungszentrum für Gesundheit und Umwelt (GmbH) Ingolstädter Landstr. 1 85764 Neuherberg www.helmholtz-muenchen.de Aufsichtsratsvorsitzende: MinDir´in Bärbel Brumme-Bothe Geschäftsführer: Prof. Dr. Günther Wess und Dr. Nikolaus Blum Registergericht: Amtsgericht München HRB 6466 USt-IdNr: DE 129521671 _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
