Hi Dave, On 29.01.2016 23:25, Dave Chinner wrote: > On Fri, Jan 29, 2016 at 11:53:35AM +0100, Christian Affolter wrote: >> Hi everyone, >> >> I'm trying to understand the differences of some bandwidth and IOPs test >> results I see while running a random-write full-stripe-width aligned fio >> test (using libaio with direct IO) on a hardware RAID 6 raw device >> versus on the same device with the XFS file system on top of it. >> >> On the raw device I get: >> write: io=24828MB, bw=423132KB/s, iops=137, runt= 60085msec >> >> With XFS on top of it: >> write: io=14658MB, bw=249407KB/s, iops=81, runt= 60182msec > > Now repeat with a file that is contiguously allocated before you > start. And also perhaps with the "swalloc" mount option. Wow, thanks! After specifying --fallocate=none (instead of the default fallocate=posix), bandwidth and iops increases and are even higher than on the raw device: write: io=30720MB, bw=599232KB/s, iops=195, runt= 52496msec I'm eager to learn what's going on behind the scenes, can you give a short explanation? Btw. mounting the volume with "swalloc" didn't make any change. Thanks a lot! Chris _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
