thanks Ryan. So in the linux cluster, there is no concept about odd number coordinate disks, which is used to deal with this issue?
anyway, probably I have to use power fencing. cheers Yu On Mon, Jun 15, 2009 at 1:36 PM, Ryan O'Hara <[email protected]> wrote: > 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 > [email protected] > https://www.redhat.com/mailman/listinfo/linux-cluster >
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