On Mon, Nov 1, 2010 at 12:53 PM, Alceu Rodrigues de Freitas Junior <glasswalk3r@yahoo.com.br> wrote:
Hello guys,

I'm looking for more information about CFS (Cluster File System) on
OpenSSI.

I already checked in the wiki, README.cfs and README.hardmounts but I'm
looking for more introductory information like how does it works, if it
uses NFS or not, etc.

Could you please provide some more info about that? A link or two would
be terrific.

Thanks in advance,
Alceu



I haven't worked on the CFS code myself, but I'm fairly sure it is NOT nfs based.  ie. NFS is not used internally in the cluster to create a CFS filesystem.

You can nfs export a CFS filesystem to computers outside the cluster, or a openSSI cluster can mount externally provided NFS share.

Thus, NFS is a way for a openSSI cluster to work with the outside world, but it is not used internally to the cluster itself.

CFS simply takes a local volume and makes it accessible as a filesystem in parallel to all the nodes in the cluster.  For failover protection, you can incorporate drbd.  drbd is not in the vanilla kernel code that openSSI is compatible with.

(ie. It went into the vanilla kernel around 2.6.32 I think which is far newer than the openSSI supported kernels).

Thus if you want CFS with failover on the cheap you should look at drbd.

You can also use CFS with externally provided raw volumes such as a FC SAN or iSCSI SAN would provide.  In that case you need to have only one node at a time accessing the raw volume.  It would in turn layer the CFS logic on top and share the volume out to the other nodes as a filesystem.

You would need to implement node failover for the access/cfs/export functionality to ensure the cluster could continue on in event of failure of the node providing the connection to the raw volume.

Greg