From: Andreas Dilger <adilger@sun.com>
To: Josef Bacik <josef@redhat.com>
Cc: "Cornelius, Martin (DWBI)" <Martin.Cornelius@smiths-heimann.com>,
linux-fsdevel@vger.kernel.org, "Roeder,
Patrick (DWBI)" <Patrick.Roeder@smithsdetection.com>
Subject: Re: Question : are concurrent write() calls with O_APPEND on local files atomic ?
Date: Wed, 19 Aug 2009 20:10:05 -0600 [thread overview]
Message-ID: <20090820021005.GZ5931@webber.adilger.int> (raw)
In-Reply-To: <20090819131749.GA7761@localhost.localdomain>
On Aug 19, 2009 09:17 -0400, Josef Bacik wrote:
> > - does this guarantee also hold for remote filesystems (nfs / smb) ?
>
> This I'm more likely to be wrong on, but I don't think so. It would be atomic
> on the local machine, but if there is somebody else on another machine writing
> to the same file I think you would probably be screwed.
With NFS at least, there is absolutely no guarantee of any kind when
multiple clients write to the same file, even with non-overlapping
writes (i.e. no O_APPEND, but application seeks to different file
offsets). That is because an NFS client does not necessarily flush
its local cache until it closes the file.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
next prev parent reply other threads:[~2009-08-20 2:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-19 12:40 Question : are concurrent write() calls with O_APPEND on local files atomic ? Cornelius, Martin (DWBI)
2009-08-19 13:17 ` Josef Bacik
2009-08-20 2:10 ` Andreas Dilger [this message]
2009-08-20 12:28 ` Trond Myklebust
2009-08-20 14:50 ` AW: Question : are concurrent write() calls with O_APPEND on localfiles " Cornelius, Martin (DWBI)
2009-08-20 15:02 ` Josef Bacik
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