On Tue, Jun 10, 2008 at 01:52:08PM -0500, Wendy Cheng wrote: > Benny Halevy wrote: > > On Jun. 10, 2008, 18:44 +0300, Wendy Cheng <s.wendy.cheng@xxxxxxxxx> wrote: > > > >> Frank Steiner wrote: > >> > >>> With the profile ignoring the FUA bit, copying or deleting directories > >>> of e.g. 10M with a about 1000 files is factor 5 faster than with the > >>> profile honoring the FUA bit. > >>> > >>> > >> FUA bit is normally combined with write-thru scsi command that bypasses > >> storage write cache. I would imagine it needs to well synchronize > >> various pieces before issuing this command. It could hurt the > >> performance if not done well, particularly for meta data. So your result > >> is not surprising. > >> > >>> We export with the "sync" option. Does that option maybe set the FUA bit > >>> for all write operations on the NFS server? > >>> > >>> > >> It depends on how the filesystem (and its associated disk subsystem) is > >> implemented. The "sync" export option itself has a heavy performance > >> impact, regardless how FUA bit is handled. Some vendors uses specialized > >> HW (e.g. NVRAM) to alleviate this performance hit. If your filesystem > >> doesn't have this type of support, you should expect "sync" option runs > >> much much slower than "async". It is a choice (or balance) between cost, > >> performance, and data reliability. > >> > > > > Wendy, I *think* what you have in mind is the sync mount option > > rather than the sync export flag. The latter just tells the server > > not to cheat and do everything asynchronously. It should *not* > > have a heavy performance penalty for I/O intensive writes if the > > client is using async writes and commits. > > > > > No, I didn't get confused ... We can use Linux as an example :) .. check > out: > http://marc.info/?l=linux-nfs&m=119618886105337&w=2 > > -- quote > > The default export might have been "async", but unless the option "sync" > in /etc/exports was being ignored I was already using "sync". Nevertheless > I will try to change to async and test if it makes a difference. > > (one day later: ) > > I have now tried it and the load on the NFS server is much lower and KDE > logins seem to be reasonably fast now. Yeah, the "async" export options is expected to improve performance on a workload like that (with lots of directory creates/deletes). But it does so by violating the promises that the protocol makes to the client. --b. ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ NFS maillist - NFS@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/nfs _______________________________________________ Please note that nfs@xxxxxxxxxxxxxxxxxxxxx is being discontinued. Please subscribe to linux-nfs@xxxxxxxxxxxxxxx instead. http://vger.kernel.org/vger-lists.html#linux-nfs -- 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
