Re: [NFS] NFS Digest, Vol 18, Issue 70 (NFS performance problems)

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Dec 03, 2007 at 04:13:02PM -0500, Wendy Cheng wrote:
> 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.

How exactly do the stale filehandles happen?

> So mirroring RPC reply cache (to another machine) 
> seems to be attractive.
>
> Any comment ? Mind I write this up and send out for discussion ?

I'd be interested?

--b.

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