On Fri, Nov 19, 2010 at 04:26:35PM -0500, Trond Myklebust wrote: > On Fri, 2010-11-19 at 15:04 -0500, J. Bruce Fields wrote: > > 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? > > If the application requests O_DIRECT/O_SYNC or calls fsync(), we are > required by POSIX to ensure the data is safe on disk. The presence of an > NFS delegation does not change that requirement. > > We could potentially relax the sync-to-disk requirements when locking > and closing the file since those are only about ensuring close-to-open > cache consistency requirements (which is also ensured by the delegation) > but we do not do so today. OK, that makes sense. We probably shouldn't say in that case that we "guarantee" the sync on close/free, if we consider it a detail of the current implementation rather than a requirement. --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
