On Tue, Jul 17, 2012 at 4:33 AM, Johnny Hughes johnny@centos.org wrote:
I always wondered why the default for nfs was ever sync in the first place. Why shouldn't it be the same as local use of the filesystem? The few things that care should be doing fsync's at the right places anyway.
Well, the reason would be that LOCAL operations happen at speeds that are massively smaller (by factors of hundreds or thousands of times) than do operations that take place via NFS on a normal network.
Everything _except_ moving a disk head around, which is the specific operation we are talking about.
If you are doing something with your network connection to make it very low latency where the speeds rival local operations, then it would likely be fine to use the exact same settings as local operations.
What I mean is that nobody ever uses sync operations locally - writes are always buffered unless the app does an fsync, and data will sit in that buffer much longer that it does on the network.