2011/5/31 djlee064 <[email protected]>: > A bit off, but can you Fyodor, and all of devs run > > dd if=/dev/null of=/cephmount/file bs=1M count=10000 (10gb) > dd if=/dev/null of=/cephmount/file bs=1M count=50000 (50gb) > dd if=/dev/null of=/cephmount/file bs=1M count=100000 (100gb) > > and continue to 200gb,... 500gb > > see the MB/s difference, expecting an enormous difference, e.g., > starts ~200MB/s and drops down to well less than 50MB/s or even less > (Depending on the #disk, but about 12MB/s per-disk is what I have > analyzed) > I feel that Fyodor's and the rest of you are testing only a very small > part, the high rate at the start is likely to be due to the journal > size.
It's client-side caching effect. Without adding the option conv=fdatasync (or fsync), dd returns the throughput without flushing the data. --Henry -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
