Re: [Evms-cluster] Access to EVMS volumes with CSM with only one node alive
Steve Dobbelstein <[email protected]> Fri, 25 Apr 2008 15:14:54 -0500
| Newsgroups | gmane.linux.evms.devel |
|---|---|
| Message-ID | <OF5096F4DA.545BFC5E-ON85257436.006E04E9-86257436.006F3D1B@us.ibm.com> |
--===============0852354409== Content-type: multipart/alternative; Boundary="0__=0ABBFEA5DFFD82798f9e8a93df938690918c0ABBFEA5DFFD8279" Content-Disposition: inline --0__=0ABBFEA5DFFD82798f9e8a93df938690918c0ABBFEA5DFFD8279 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: quoted-printable Maximilian Wilhelm <[email protected]> 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 i= s 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 clus= ter 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 ot= her node. If the other node is alive, which one is in the membership and w= hich one is not? If both nodes are up but cannot talk to each other, neithe= r 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 soluti= on. I have heard that there are some implementations or scenarios that allo= w 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.= --0__=0ABBFEA5DFFD82798f9e8a93df938690918c0ABBFEA5DFFD8279 Content-type: text/html; charset=US-ASCII Content-Disposition: inline Content-transfer-encoding: quoted-printable <html><body> <p><tt>Maximilian Wilhelm <[email protected]></tt><tt> w</tt><= tt>rote on 04/25/2008 01:15:48 PM:<br> <br> > Hi!<br> > <br> > I've set up a Xen-Cluster with two nodes sharing some SAN storage.= <br> > <br> > I decided to use EVMS to cut on of the LUNs into pieces for the Do= mU<br> > storage. So I put a CSM on the LUN devices, and some LVM stuff in<= br> > there.<br> > <br> > If I now reboot/poweroff one node for any reason, the /dev/evms/..= .<br> > devices managent by CSM on the running node disappear, which is qu= ite<br> > bad as I cannot start Xen DomUs when one node failed.<br> > <br> > Is this intentional or can I do anything about that?<br> > <br> > I can't imagine any reason for this behaviour and would realy like= to<br> > be able to use the volumes if only one node is alive.<br> > <br> > Ciao<br> > Max<br> > -- <br> > Follow the white penguin.<br> </tt><br> <tt>Hi, Max.</tt><br> <br> <tt>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.</tt><br> <br> <tt>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. &= nbsp;All that the node can determine is that it cannot talk to the othe= r 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, wh= ich 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 i= s the one in the membership and that the other node isn't. The ty= pical way to handle the scenario is to have the node declare itself as = not being in the membership. This is the safe solution. I h= ave heard that there are some implementations or scenarios that allow o= ne node to have then membership, but I don't recall the specifics.</tt>= <br> <br> <tt>If you want to check if your node is in the membership, run "e= vmsccm -l". The evmsccm command is used by EVMS to determine= if a node is in the membership. The "-l" switch says t= o list the nodes in the membership.</tt><br> <br> <tt>Hope this helps.</tt><br> <br> <tt>Steve D.</tt></body></html>= --0__=0ABBFEA5DFFD82798f9e8a93df938690918c0ABBFEA5DFFD8279-- --===============0852354409== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. 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