On 04/08/16 06:56 PM, Dan Swartzendruber wrote: > I'm setting up an HA NFS server to serve up storage to a couple of > vsphere hosts. I have a virtual IP, and it depends on a ZFS resource > agent which imports or exports a pool. So far, with stonith disabled, > it all works perfectly. I was dubious about a 2-node solution, so I > created a 3rd node which runs as a virtual machine on one of the hosts. > All it is for is quorum. So, looking at fencing next. The primary > server is a poweredge R905, which has DRAC for fencing. The backup > storage node is a Supermicro X9-SCL-F (with IPMI). So I would be using > the DRAC agent for the former and the ipmilan for the latter? I was > reading about location constraints, where you tell each instance of the > fencing agent not to run on the node that would be getting fenced. So, > my first thought was to configure the drac agent and tell it not to > fence node 1, and configure the ipmilan agent and tell it not to fence > node 2. The thing is, there is no agent available for the quorum node. > Would it make more sense instead to tell the drac agent to only run on > node 2, and the ipmilan agent to only run on node 1? Thanks!
This is a common mistake. Fencing and quorum solve different problems and are not interchangeable. In short; Fencing is a tool when things go wrong. Quorum is a tool when things are working. The only impact that having quorum has with regard to fencing is that it avoids a scenario when both nodes try to fence each other and the faster one wins (which is itself OK). Even then, you can add 'delay=15' the node you want to win and it will win is such a case. In the old days, it would also prevent a fence loop if you started the cluster on boot and comms were down. Now though, you set 'wait_for_all' and you won't get a fence loop, so that solves that. Said another way; Quorum is optional, fencing is not (people often get that backwards). As for DRAC vs IPMI, no, they are not two things. In fact, I am pretty certain that fence_drac is a symlink to fence_ipmilan. All DRAC is (same with iRMC, iLO, RSA, etc) is "IPMI + features". Fundamentally, the fence action; rebooting the node, works via the basic IPMI standard using the DRAC's BMC. To do proper redundant fencing, which is a great idea, you want something like switched PDUs. This is how we do it (with two node clusters). IPMI first, and if that fails, a pair of PDUs (one for each PSU, each PDU going to independent UPSes) as backup. -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? _______________________________________________ Users mailing list: Users@clusterlabs.org http://clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org