On Sun, Nov 28, 2010 at 6:17 AM, Ashish Verma <[email protected]> wrote: > They have shown GFS servers over iScsi servers and mentioned the benefits of > single file-system over the multiple block device paths thereby providing > redundancy. However cant the same be achieved with NFS by placing nfs over > the multiple iscsi servers and still you would get the same results.
On the NFS servers, how will you mount the shared iSCSI volume? Which FS will you use to format the iSCSI volume? Ext3/etc are not cluster aware, ie, you cannot mount the same block device from multiple servers at the same time. NFS is not a true file system -- it's only the means of exporting a backend FS on to the network. Unless you have a cluster aware FS on the backend which is shared across multiple servers, you will end up with independent storage islands for each NFS server. It is also not best practice to take a backend cluster FS and re-export it using NFS/CIFS. This typically breaks Unix file locking semantics. Best option is to use cluster aware file systems like GFS, Luster, Coda, StorNext (proprietary) end to end. NFS has addressed this lack of parallelism in version 4.1 -- see pNFS. pNFS provides multiple data paths for the block access to increase performance, while meta data is on a single server as before. You still need a shared backend storage and FS anyway. - Raja _______________________________________________ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
