On Wed, Apr 01, 2015 at 11:02:17AM -0700, lyndat3@xxxxxxxxxxxxx wrote: > > There's no maximum sync/async ratio. You could make that ratio lower or > > higher by varying dd's block size, for example. > > > > The way I'd look at it, your dd of a 100MB file above is doing 3072 > > writes, and taking about 8*60/3072 =~ .16 seconds per write. > > > > That does sound high. Things to look at to understand why might include > > the round-trip ping time to the server, and the time for the server's > > disk to do a synchronous write. > > > > After comments from one of the nfs client maintainers, it turns out the slowness issue is simply one of not-quite-MIS-configuration. > > As helpfully commented here > > http://serverfault.com/questions/499174/etc-exports-mount-option/500553#500553 > > , IIUC there are two *separate* syncs to consider -- at the server, and at the client. > > 'sync' on the EXPORT, and 'async' on the MOUNT is the sane approach; That config also appears to return the performance. > > The many recommendations online to use 'sync' for data integrity are IIUC for sync on the server. Yes. This is a common source of confusion. In retrospect maybe the export sync/async option should have had a different name from the client mount option.--b. > With 'async' set on the moount, and 'sync' on the exports, It appears integrity of writes is properly assured and I've got rsync-over-NFSv4 performance back in the ~30-60 MB/s range. > > LT -- 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
