On Sun, Jun 14, 2009 at 11:21:08AM +1000, yu song wrote: > Hi, > > I am planning to build a 2 nodes cluster on rhcl 5.3, and looking for what > fencing method I could use. > > On the storage side, it is EMC clarion and supports scsi 3 reservation. > > So I'm thinking to use fence_scsi agent to do the disk fencing. however, > according the redhat website, it states that fence_scsi does not support > two nodes cluster. > > Could anyone kindly explain it why? (never had this issue when use veritas > cluster) In a 2 node cluster, fencing becomes a race -- the node fences the other node first wins. This works well with power fencing, but not so well with SAN fencing (eg. fence_scsi). The problem with fence_scsi in a 2 node cluster is this: Suppose we have 2 node, call them A and B. Also assume we have multple LUNs, which we will call lun1, lun2, lun3. Consider what happens when a network partition occurs -- both nodes attempt to fence one another. It is possible that A could remove B's key from lun1 and lun2, but node B could remove node A's key from lun3. This is inconsistent and there is no clear "winner". Ryan -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
