Hello Greg, On 01/10/2011 01:38 PM, [email protected] wrote: > While a third idle node in the cluster is a way to regulate the quorum votes, > you're right in that it's not very economical. > > A way to keep the quorum device from being an SPOF is to assure it is > multipathed as well. However, by default, the quorum code does not define > the device from its multipathed name. Instead, it defaults to the dm-# which > we've proven in the past does not retain its name through reboots or rescans. > What you need to do is get the disk ID number of the shared quorum disk > itself, and create an alias name for it in multipath.conf: > ... > multipaths { > multipath { > wwid 36006016338602300ca974b4b1b7edf11 > alias qdisk > } > ... This will not eleminate the SPOF using one ONE storage... What I meant is using at least two storage devices in different locations i.e. DCs. I'll assume serious SAN connections are always using multipath ;) And by the way, I would prefer using the qdisc-label - which should be unique and is scanned during start of qdiscd. > > ...then define it in cluster.conf with a device="/dev/mapper/qdisk" in the > quorumd stanza. When you enter a clustat, your qdisk should show up like > this: > > /dev/mapper/qdisk 0 Online, Quorum Disk > > You can test this by disconnecting one of your SAN connections, and watch the > cluster log. It will show a loss of communication with the quorum disk for a > few seconds and then return to normal. ... and qdisc will fail if the underlaying SAN device got lost - f.e. power failure in one DC. As already said, SAN-storage will be mirrored to two DCs using cmirorror, but this is not possible for the qdisc.
Thanks for your answer, anyways. > > > Regards; > Greg Charles > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Andreas Bleischwitz > Sent: Monday, January 10, 2011 5:25 AM > To: [email protected] > Subject: [Linux-cluster] Howto define two-node cluster in enterprise > environment > > Hello list, > > I recently ran into some questions regarding a two-node cluster in an > enterprise environment, where single-point-of-failures were tried to be > eliminated whenever possible. > > The situation is the following: > Two-node cluster, SAN-based shared storage - multipathed; host-based > mirrored, bonded NICS, Quorum device as tie-breaker. > > Problem: > The quorum device is the single-point-of-failure as the SAN-device could fail > and hence the quorum-disc wouldn't be accessible. > The quorum-disc can't be host-based mirrored, as this would require cmirror - > which depends on a quorate cluster. > One solution: use storage-based mirroring - with extra costs, limited to no > support with mixed storage vendors. > Another solution: Use a third - no service - node which has to have the same > SAN-connections as the other two nodes out of cluster reasons. This node will > idle most of the time and therefore be very uneconomic. > > How are such situations usually solved using RHCS? There must be a way of > configuring a two-nodecluster without having a SPOF defined. > > HP had a quorum-host with their no longer maintained Service Guard, which > could do quorum for more than on cluster at once. > > Any suggestions appreciated. > > Best regrads, > > Andreas Bleischwitz > > -- > Linux-cluster mailing list > [email protected] > https://www.redhat.com/mailman/listinfo/linux-cluster -- Linux-cluster mailing list [email protected] https://www.redhat.com/mailman/listinfo/linux-cluster
