NFS multipathing
I would like to see NFS multipathing.
Quite possibly this would work properly with only client side development. By that i mean that the NFS server almost certainly wouldnt know that its going on, except maybe with locking.
Essentially, the mount command might somehow be told that two servers:/exports are the same thing.
mount -o secondary="serverip2:/vol/export" serverip1:/vol/export /mnt/point
Responses
I like this idea. We might be better off with
mount server1:/vol/export,server2:/vol/export,...,serverN:/vol/export /mnt
Say you have four servers w/ GFS2 exporting via NFS. You can vary this order among clients to achieve a poor-man's load balancing while getting the effect you want.
Perhaps:
mount server1,server2,server3:/vol/export
can be a short-hand to suggest that the mount point is the same on all servers. We'd probably need some sort of retry count as well:
mount -t nfs -o retry=1,timeout=5 ...
Only attempt one retry connection per host listed (per loop of the host list). Any mount attempt must succeed within 5 seconds. If the client can be modified to cycle through hosts like this, we'll definitely need to be able to set some parameters to make the failover happen in a reasonable amount of time.
EDIT @ 12:17, 07/27: Since we're not really "re-mounting" I wonder how the client would be modified to try re-establishing a connection to a new server. Will the mtab entry be modified to reflect the fact that we're now send/recv traffic to/from a different server?
Then, of course, what is the behavior for hard vs. soft mounts?
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