Ceph

In one of our tests, volume write bandwidth drops to 1/9 with 'journaling' enabled as shown in the attachments.

Any ideas?

[root@node102 ~]# rbd info volumes/volume-956a9d4b-7642-4f81-919b-ef80148e279d
rbd image 'volume-956a9d4b-7642-4f81-919b-ef80148e279d':
size 16384 MB in 4096 objects
order 22 (4096 kB objects)
block_name_prefix: rbd_data.5e62212f072d
format: 2
features: layering, exclusive-lock
flags:

[root@zlq-master-test ~]# dd if=/dev/zero of=/dev/vdc bs=1M count=200
200+0 records in
200+0 records out
209715200 bytes (210 MB) copied, 2.25493 s, 93.0 MB/s
------------------------------------------------------------------------------------------------------------
[root@node102 ~]# rbd info volumes/volume-956a9d4b-7642-4f81-919b-ef80148e279d
rbd image 'volume-956a9d4b-7642-4f81-919b-ef80148e279d':
size 16384 MB in 4096 objects
order 22 (4096 kB objects)
block_name_prefix: rbd_data.5e62212f072d
format: 2
features: layering, exclusive-lock, journaling
flags:
journal: 5e62212f072d
mirroring state: disabled

[root@zlq-master-test ~]# dd if=/dev/zero of=/dev/vdc bs=1M count=200
200+0 records in
200+0 records out
209715200 bytes (210 MB) copied, 18.953 s, 11.1 MB/s