From: Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: RE: Mount wsize and sync options
Date: Wed, 19 May 2004 15:41:51 -0400
Sender: nfs-admin@lists.sourceforge.net
Message-ID: <1084995711.4223.99.camel@lade.trondhjem.org>
References: <013201c43dde$ca448a20$0f01a8c0@CARTMAN>
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Cc: nfs@lists.sourceforge.net
To: Amir Hermelin <amir@montilio.com>
In-Reply-To: <013201c43dde$ca448a20$0f01a8c0@CARTMAN>
Errors-To: nfs-admin@lists.sourceforge.net

P=E5 on , 19/05/2004 klokka 16:20, skreiv Amir Hermelin:
> Yes, It does accept 1 or 2k.  What's the reason for limiting synced write=
s
> to page size?

It is because the VFS only writes one page at a time.

Now you could cluster those pages into one large RPC request (and this
is how O_SYNC normally works), but it turns out that some applications
do actually depend on the pages being synced to disk in the particular
order that they were written. The clustering technique unfortunately has
races that can ruin those ordering guarantees.

Cheers,
  Trond


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