Re: O_DIRECT, O_SYNC, or fsync() on NFS mounts?

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

On Fri, Nov 19, 2010 at 02:24:59PM -0500, Trond Myklebust wrote:
> On Thu, 2010-11-18 at 15:34 -0800, Moazam Raja wrote:
> > Hi all,
> > 
> > I'm currently exporting a ZFS filesystem on Solaris 11 Express as NFS.
> > I have a Linux client mounting that NFS v3 filesystem with the
> > proto=tcp option.
> > 
> > My question is, what's the safest and most reliable way to write data
> > to this NFS mount on a Linux client? Should my application code use
> > O_DIRECT, or O_SYNC? Or should I be doing a write() and a fsync()? I
> > want to make sure that data is not lost and is truly committed, while
> > keeping decent performance (of course).
> 
> Any one of the above methods will ensure that the data is synced to
> disk. In addition, NFS also guarantees that your data is fully synced to
> disk when taking/freeing POSIX locks, and when you close() the file.

Is the client still doing that in the presence of a write delegation, by
the way?

--b.

> 
> The choice of one method over the other depends on your application
> requirements. Not on your choice of underlying storage.
> 
> Trond
> 
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