Bob Friesenhahn writes: > On Wed, 29 Jul 2009, Jorgen Lundman wrote: > > > > For example, I know rsync and tar does not use fdsync (but dovecot does) > > on > > its close(), but does NFS make it fdsync anyway? > > NFS is required to do synchronous writes. This is what allows NFS > clients to recover seamlessly if the server spontaneously reboots. > If the NFS client supports it, it can send substantial data (multiple > writes) to the server, and then commit it all via an NFS commit.
In theory; but for lots of single threaded file creation (the tar process) the NFS server is fairly constrained in what it can do. We need something like directory delegation to allow the client to interact with local caches like a DAS filesystem can. A slog on SDD can help, but that SSD needs to have low latency writes, which typically implies DRAM buffers, and a capacitor so that it can be made to ignore cache flushes. -r > Note that this requires more work by the client since the NFS client > is required to replay the uncommited writes if the server goes away. > > > Sorry for the giant email. > > No, thank you very much for the interesting measurements and data. > > Bob > -- > Bob Friesenhahn > bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ > GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
