On Mon, Aug 9, 2010 at 8:23 PM, Xiaoguang Liu <syslxg@xxxxxxxxx> wrote: > on my 2-ods-node cluster, dd can only reach 13MB/s on rbd device. this > is much lower than what I expected. > I can get 30-60 MB/s on a ceph filesystem over the same cluster. > > any idea? > It is hard to really know without more info, just note that when you write directly to the block device you bypass any caches, as you do a raw write. So it is expected that you'd notice a performance drop. You can try running 'iostat -x 1', it should give some idea about what's going on. Thanks, Yehuda -- 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
