Date: Thu, 7 Apr 2005 14:46:45 -0700 (PDT) From: Mohan Srinivasan <mohan_srinivasan@yahoo.com> To: dart@nersc.gov, Charles Swiger <cswiger@mac.com> Cc: freebsd-net@freebsd.org Subject: Re: Disable NFS client cache (or other traffic reduction methods) Message-ID: <20050407214645.65599.qmail@web80604.mail.yahoo.com> In-Reply-To: 6667
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Hi, Unfortunately, there's no way in the FreeBSD NFS client to disable data caching. Setting the ac* values to 0 will have the effect of disabling the attribute cache, which means that you'll never fetch attributes from the cache, but force an over-the-wire getattr call each time. But this does not disable data caching. For reference, take a look at nfs_loadattrcache() and nfs_getattrcache(). The real reason for tweaking the ac* values is to improve on the consistency of the cached data (for applications with data shared across multiple clients). By setting the ac* values to 0 and bypassing attr caching completely, you force much more frequent mtime checks giving you much better consistency of the cached data. I added Direct IO support for the NFS client for exactly this reason - to bypass data caching. But I tickled a bug in the -current NFS server when I use Direct IO on the client and I have left it disabled until I get a chance to fix that bug. Direct IO support works fine when used against a FreeBSD 4.x NFS server or a NetApp filer. mohan --- Eli Dart <dart@nersc.gov> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > > >> Is there a way to disable client-side caching? I've looked, and > >> can't seem to find one. Or, do I have this wrong and there is > >> something else that is causing this? > > > > > > Take a look through "man mount_nfs" for: > > > > -a Set the read-ahead count to the specified value. This may > > be in > > the range of 0 - 4, and determines how many blocks will be > > read > > ahead when a large file is being read sequentially. Trying a > > value greater than 1 for this is suggested for mounts with a > > large bandwidth * delay product. > > I did see this. Since the client is not reading any files (I think > all the reads are being done by the NFS layer, not by any userland > processes with open files) I had ignored -a. > > > > > ...and the -o ac*** options. Although you may be right-- I was a bit > > surprised not to see a "-o noac", myself. Solaris has one: > > Hmmmm.....any NFS gurus know whether setting the ac* options to 0 > will disable client caching? Or, will setting these to 0 result in > the client NFS layer fetching the data from the server and then > immediately expiring it? > > Thanks, > > --eli > > > > > > > noac Suppress data and attribute caching. > > > > :-) > > > > - -- > > - ------------------------------------------------------------------- > Eli Dart Office: (510) 495-2999 > NERSC Center Networking and Security Group Cell: (510) 703-4508 > Lawrence Berkeley National Laboratory Fax: (510) 486-4316 > PGP Fingerprint = C970 F8D3 CFDD 8FFF 5486 343A 2D31 4478 5F82 B2B3 > - ------------------------------------------------------------------- > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.0 (MingW32) > Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org > > iD4DBQFCVZYOLTFEeF+CsrMRAlReAKDMxrs97SSkZJRhaEVxRRpO51XrsACXX983 > grAaYcgINLwiLtzoz3nLhQ== > =GAZ7 > -----END PGP SIGNATURE----- > > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >
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