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From: Maximilian Wilhelm <max@rf...> - 2008-04-25 18:16:09
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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. |
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From: Steve Dobbelstein <steved@us...> - 2008-04-25 20:16:15
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Maximilian Wilhelm <max@...> 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. Hope this helps. Steve D. |
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From: Thomas Guyot-Sionnest <thomas@za...> - 2008-04-29 15:52:23
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Steve Dobbelstein wrote: | Maximilian Wilhelm <max@...> 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----- |
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From: Maximilian Wilhelm <max@rf...> - 2008-07-17 22:32:11
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Anno domini 2008 Thomas Guyot-Sionnest scripsit: Hi! Sorry for the really long delay, I've been occupied with other projects. [EVMS CSM does not activate volumes when only one node is active] > 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 :) Could you please share your configuration? In my setup I don't use stonith as I have two Xen servers just sharing a SAN LUN for storage, so I don't see a need for stonith. I would just like to be able to use the EVMS cluster volumes on any node at any time. Thanks for your help! Ciao Max -- Follow the white penguin. |