From: Trond Myklebust Subject: Re: NFS performance (Currently 2.6.20) Date: Wed, 06 Feb 2008 13:46:25 -0500 Message-ID: <1202323586.8549.18.camel@heimdal.trondhjem.org> References: <3093.195.41.66.226.1202292274.squirrel@mail.jabbernet.dk> <47A9C620.70106@oxeva.fr> <1202311096.12647.28.camel@heimdal.trondhjem.org> <47A9FB75.90206@oxeva.fr> Mime-Version: 1.0 Content-Type: text/plain Cc: Jesper Krogh , linux-nfs@vger.kernel.org To: Gabriel Barazer Return-path: Received: from pat.uio.no ([129.240.10.15]:39540 "EHLO pat.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751468AbYBFSqa (ORCPT ); Wed, 6 Feb 2008 13:46:30 -0500 In-Reply-To: <47A9FB75.90206-KSe8qvLY914@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Wed, 2008-02-06 at 19:24 +0100, Gabriel Barazer wrote: > Oops (tm)! Fortunately I do mostly reads, but maybe the exports(5) man > page should be updated. According to the man page, I thought that > although writes aren't commited to the block devices, the server-side > cache is correctly synchronized (but lost if you pull the plug). ...or if the server crashes for some reason. > Thanks > for the explanation. Having a battery backed large write cache on the > server, is there a performance hit when switching from async to sync in > NFSv3 ? The main performance hits occur on operations like create(), mkdir(), rename and unlink() since they are required to be immediately synced to disk. IOW: there will be a noticeable overhead when writing lots of small files. For large files, the overhead should be minimal, since all writes can be cached by the server until the close() operation. Trond