> Hi, > > > My goal is 4 OSD's, each on separate machines, with 1 drive in each for a > start, but I want to see performance of at least the same order of magnitude > as the theoretical maximum on my hardware before I think about replacing > my existing setup. > > My current understanding is that it's not even possible, you always > have a min 2/3x slow down in the best case. > > If you do sustained sequential write benchmark, and have a single > drive, then that drive ends up writing the data twice (journal + final > storage area) which with the seeks will more than divide by 2 the peak > perf of the drive. And since it's sequential, it will only write to 1 > PG at a time (so not divided among several OSD). > > Also AFAIU the OSD receiving the data will also have to send the data > to the other OSD in the PG and wait for them to say everything is > written before confirming the write, which slows it even more. > Correct, but that's the theoretical maximum I was referring to. If I calculate that I should be able to get 50MB/second then 30MB/second is acceptable but 500KB/second is not :) James -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
