For better or worse, I can repeat your "ioping" findings against a qcow2 image hosted on a krbd-backed volume. The "bad" news is that it actually isn't even sending any data to the OSDs -- which is why your latency is shockingly low. When performing a "dd ... oflag=dsync" against the krbd-backed qcow2 image, I can see lots of IO being coalesced from 4K writes into larger writes, which is artificially inflating the stats. On Mon, Oct 31, 2016 at 11:08 AM, Bill WONG <wongahshuen@xxxxxxxxx> wrote: > Hi Jason, > > it looks the situation is the same, no difference. my ceph.conf is below, > any comments or improvement required? > --- > [global] > fsid = 106a12b0-5ed0-4a71-b6aa-68a09088ec33 > mon_initial_members = ceph-mon1, ceph-mon2, ceph-mon3 > mon_host = 192.168.8.11,192.168.8.12,192.168.8.13 > auth_cluster_required = cephx > auth_service_required = cephx > auth_client_required = cephx > filestore_xattr_use_omap = true > osd pool default size = 3 > osd pool default min size = 1 > osd pool default pg num = 4096 > osd pool default pgp num = 4096 > osd_crush_chooseleaf_type = 1 > mon_pg_warn_max_per_osd = 0 > max_open_files = 131072 > > [mon] > mon_data = /var/lib/ceph/mon/ceph-$id > > mon clock drift allowed = 2 > mon clock drift warn backoff = 30 > > [osd] > osd_data = /var/lib/ceph/osd/ceph-$id > osd_journal_size = 20000 > osd_mkfs_type = xfs > osd_mkfs_options_xfs = -f > filestore_xattr_use_omap = true > filestore_min_sync_interval = 10 > filestore_max_sync_interval = 15 > filestore_queue_max_ops = 25000 > filestore_queue_max_bytes = 10485760 > filestore_queue_committing_max_ops = 5000 > filestore_queue_committing_max_bytes = 10485760000 > journal_max_write_bytes = 1073714824 > journal_max_write_entries = 10000 > journal_queue_max_ops = 50000 > journal_queue_max_bytes = 10485760000 > osd_max_write_size = 512 > osd_client_message_size_cap = 2147483648 > osd_deep_scrub_stride = 131072 > osd_op_threads = 8 > osd_disk_threads = 4 > osd_map_cache_size = 1024 > osd_map_cache_bl_size = 128 > osd_mount_options_xfs = "rw,noexec,nodev,noatime,nodiratime,nobarrier" > osd_recovery_op_priority = 4 > osd_recovery_max_active = 10 > osd_max_backfills = 4 > rbd non blocking aio = false > > [client] > rbd_cache = true > rbd_cache_size = 268435456 > rbd_cache_max_dirty = 134217728 > rbd_cache_max_dirty_age = 5 > --- > > > > On Mon, Oct 31, 2016 at 9:20 PM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote: >> >> On Sun, Oct 30, 2016 at 5:40 AM, Bill WONG <wongahshuen@xxxxxxxxx> wrote: >> > any ideas or comments? >> >> Can you set "rbd non blocking aio = false" in your ceph.conf and retry >> librbd? This will eliminate at least one context switch on the read IO >> path -- which result in increased latency under extremely low queue >> depths. >> >> -- >> Jason > > -- Jason _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
 |