Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On 25.11.2011 17:08, John Lauro wrote: > What I’m not sure about from the examples… Can you then add more > GFS/OCFS2 nodes (ie: a 3^rd and 4^th node) that have no local disk as > part of the SAN cluster, but instead talk drbd to the first two nodes? > Or would you have to run a shared failover service such as NFS on top of > the two node cluster if you need multiple hosts accessing it? For OCFS or GFS, all nodes need access to the same block device at the same time. In a two-node setup, you can easily use DRBD in dual-primary mode to provide such a shared block device. For more than two nodes, you need to export the block device provided by DRBD by a different method (such as iSCSI), since DRBD (normaly) supports only two nodes to share a block device. Depending on your needs, you can either go for an active-passive or an active-active export of the DRBD device(s). Active-passive is way easier to implement. Try Google for "DRBD iSCSI" and you'll find some interesting readings on that. Generally this route involves DRBD in single-primary mode, iSCSI target/initiator implementations, a method to share an IP addresses and a cluster manager to coordinate all those things. The active-active route seems to be somewhat harder - or at least I did not find any useful references. A possible implementation would likely include all of the above, except that one would use SCSI-multipath instead of sharing a single IP address to access the iSCSI targets. @list: did anybody try such a thing ? > > Mainly ask because I assume recovery time from failover would be much > quicker with a cluster filesystem (doesn’t have to fsck/remount), and > reads (would?) be split over the two hosts instead of just one, so it > should be slightly faster with two hosts serving read I/O requests > instead of one. In an active-passive setup, you won't get any performance gains. Whether you can see any throughput improvements with an active-active setup would basically depend on your network setup.