From: Thomas Guyot-S. <th...@za...> - 2008-04-29 15:52:23
|
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Steve Dobbelstein wrote: | Maximilian Wilhelm <ma...@rf...> wrote on 04/25/2008 01:15:48 PM: | | > Hi! | > | > I've set up a Xen-Cluster with two nodes sharing some SAN storage. | > | > I decided to use EVMS to cut on of the LUNs into pieces for the DomU | > storage. So I put a CSM on the LUN devices, and some LVM stuff in | > there. | > | > If I now reboot/poweroff one node for any reason, the /dev/evms/... | > devices managent by CSM on the running node disappear, which is quite | > bad as I cannot start Xen DomUs when one node failed. | > | > Is this intentional or can I do anything about that? | > | > I can't imagine any reason for this behaviour and would realy like to | > be able to use the volumes if only one node is alive. | > | > Ciao | > Max | > -- | > Follow the white penguin. | | Hi, Max. | | The EVMS CSM will not display any shared storage on a node if that node | is not in the membership of the cluster. The reason is that if the node | is not in the membership then the CSM cannot guarantee that the node can | safely access the shared storage. | | Last I heard it was still undecided if a single node in a two node | cluster can declare that it is part of the membership of the cluster. | All that the node can determine is that it cannot talk to the other | node. It doesn't know if it is the only one alive or if it lost its | connection to the other node. If the other node is alive, which one is | in the membership and which one is not? If both nodes are up but cannot | talk to each other, neither one can declare that it is the one in the | membership and that the other node isn't. The typical way to handle the | scenario is to have the node declare itself as not being in the | membership. This is the safe solution. I have heard that there are | some implementations or scenarios that allow one node to have then | membership, but I don't recall the specifics. | | If you want to check if your node is in the membership, run "evmsccm | -l". The evmsccm command is used by EVMS to determine if a node is in | the membership. The "-l" switch says to list the nodes in the membership. I'm using EVMS CSM's in a 2-node Linux-HA cluster (Linux-HA v2.x with v1 config) and I don't have any problem with single node. If one node gracefully quits (/etc/init.d/heartbeat shutdown) the other node keeps membership. If communication breaks the other node gets gets STONITH'ed instead (using both serial & udp for communication). Also if I start a node and it can't communicate with the other one it will STONITH it before taking resources. For that reason I don't start heartbeat on bootup to avoid possibility of broken communication causing nodes to kill each other in a round-robin way :) - -- Thomas -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFIF0Qa6dZ+Kt5BchYRAhHkAKC02Tcij0G1HkqseKymi/GvWN96+QCgwx/W w5CFNK+pbkMNrTd0KjJOlw0= =MhTk -----END PGP SIGNATURE----- |