J. Bruce Fields wrote: > On Fri, Nov 30, 2007 at 11:27:16AM -0500, Wendy Cheng wrote: > >> Well, a dumb question from me (borrowing Bruce's line :) ) ... even with >> "sync" in place, when server rebooted, the RPC reply cache is gone. How >> does linux server handle re-transmitted non-idempotent requests ? >> > > Badly! > > Somebody should figure out whether it would be possible for us to > implement persistent sessions in v4.1: > > > http://www.nfsv4-editor.org/draft-17/draft-ietf-nfsv4-minorversion1-17.html#Persistence > > It looks hard! > Or use cluster (a backup server is quite affordable nowadays) ? Was about to kick off a new discussion about this ...
I did a prototype about 4 years ago on 2.4 kernel where the RPC reply cache (slightly modified to include raw NFS request packets) was mirrored by backup server (in memory). The reply was delayed to go back to client until the mirrored reply cache entry was acknowledged by the backup server. Upon crash, the backup server piggybacked its logic on ext3's journal recovery code. For reply cache entries not replayed or not recognized by jbd, nfsd resent the NFS raw requests down to filesystem just like any new arrived requested. The prototype code was able to gain at least 70% of the async mode performance without losing the data. One of other issues with our current linux-based NFS cluster failover is also right in this arena - that is, upon failover, the non-idempotent could introduce stale filehandle errors that have been causing headaches with some of the applications. So mirroring RPC reply cache (to another machine) seems to be attractive. Any comment ? Mind I write this up and send out for discussion ? -- Wendy ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ NFS maillist - [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/nfs _______________________________________________ Please note that [EMAIL PROTECTED] is being discontinued. Please subscribe to [email protected] instead. http://vger.kernel.org/vger-lists.html#linux-nfs - To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
