On Wed, Aug 26, 2015 at 6:22 PM, Haomai Wang <haomaiwang@xxxxxxxxx> wrote: > On Wed, Aug 26, 2015 at 11:16 PM, huang jun <hjwsm1989@xxxxxxxxx> wrote: >> hi,all >> we create a 2TB rbd image, after map it to local, >> then we format it to xfs with 'mkfs.xfs /dev/rbd0', it spent 318 >> seconds to finish, but local physical disk with the same size just >> need 6 seconds. >> > > I think librbd have two PR related to this. > >> After debug, we found there are two steps in rbd module during formating: >> a) send 233093 DELETE requests to osds(number_of_requests = 2TB / 4MB), >> this step spent almost 92 seconds. > > I guess this(https://github.com/ceph/ceph/pull/4221/files) may help It's submitting deletes for non-existent objects, not zeroing. The only thing that will really help here is the addition of rbd object map support to the kernel client. That could happen in 4.4, but 4.5 is a safer bet. > >> b) send 4238 messages like this: [set-alloc-hint object_size 4194304 >> write_size 4194304,write 0~512] to osds, that spent 227 seconds. > > I think kernel rbd also need to use > https://github.com/ceph/ceph/pull/4983/files set-alloc-hint may be a problem, but I think a bigger problem is the size of the write. Are all those writes 512 bytes long? Thanks, Ilya -- 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
