On 20 December 2015 at 22:47, Yan, Zheng <uker...@gmail.com> wrote: > >> --------------------------------------------------------------- > >> > > > fio tests AIO performance in this case. cephfs does not handle AIO > properly, AIO is actually SYNC IO. that's why cephfs is so slow in > this case. > > Regards > Yan, Zheng > > OK, so i changed fio engine to 'sync' for the comparison of a single underlying osd vs the cephfs.
the cephfs w/ sync is ~ 115iops / ~500KB/s. the underlying osd storage w/ sync is 6500 iops/270MB/s. I also don't think this explains why cephfs-fuse faster (~5x faster, but still ~100x slower than it should be). If i get rid of fio and use tried-and-true dd: time dd if=/dev/zero of=rw.data bs=256k count=10000 on the underlying osd storage shows 426MB/s. on the cephfs, it gets 694MB/s. hmm. so i guess my 'lag' issue of slow requests is unrelated and is my real problem.
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