Re: Librbd performance VS KRBD performance

赵赵贺东 <zhaohedong@xxxxxxxxx> · Thu, 15 Nov 2018 14:03:44 +0800

Thank you for your attention.

Our test are in run in physical machine environments.
Fio for KRBD:
[seq-write]
description="seq-write"
direct=1
ioengine=libaio
filename=/dev/rbd0
numjobs=1
iodepth=256
group_reporting
rw=write
bs=4M
size=10T
runtime=180

*/dev/rbd0 mapped by rbd_pool/image2, so KRBD & librbd fio test use the same image.

Fio for librbd:
[global]
direct=1
numjobs=1
ioengine=rbd
clientname=admin
pool=rbd_pool
rbdname=image2
invalidate=0    # mandatory
rw=write
bs=4M
size=10T
runtime=180

[rbd_iodepth32]
iodepth=256

Image info:
rbd image 'image2':
	size 50TiB in 13107200 objects
	order 22 (4MiB objects)
	data_pool: ec_rbd_pool
	block_name_prefix: rbd_data.8.148bb6b8b4567
	format: 2
	features: layering, data-pool
	flags: 
	create_timestamp: Wed Nov 14 09:21:18 2018

* data_pool is a EC pool

Pool info:
pool 8 'rbd_pool' replicated size 2 min_size 1 crush_rule 0 object_hash rjenkins pg_num 256 pgp_num 256 last_change 82627 flags hashpspool stripe_width 0 application rbd
pool 9 'ec_rbd_pool' erasure size 6 min_size 5 crush_rule 4 object_hash rjenkins pg_num 256 pgp_num 256 last_change 82649 flags hashpspool,ec_overwrites stripe_width 16384 application rbd

Rbd cache: Off (Because I think in tcmu , rbd cache will mandatory off, and our cluster will export disk by iscsi in furture.) 

Thanks!

在 2018年11月15日，下午1:22，Gregory Farnum <gfarnum@xxxxxxxxxx> 写道：

You'll need to provide more data about how your test is configured and run for us to have a good idea. IIRC librbd is often faster than krbd because it can support newer features and things, but krbd may have less overhead and is not dependent on the VM's driver configuration in QEMU...

On Thu, Nov 15, 2018 at 8:22 AM 赵赵贺东 <zhaohedong@xxxxxxxxx> wrote:
Hi cephers,

All our cluster osds are deployed in armhf.

Could someone say something about what is the rational performance rates for librbd VS KRBD ?

Or rational performance loss range when we use librbd compare to KRBD.

I googled a lot, but I could not find a solid criterion.  

In fact , it confused me for a long time.

About our tests:

In a small cluster(12 osds), 4m seq write performance for Librbd VS KRBD is about 0.89 : 1 (177MB/s : 198MB/s ). 

In a big cluster (72 osds), 4m seq write performance for Librbd VS KRBD is about  0.38: 1 (420MB/s : 1080MB/s).

We expect even increase  osd numbers, Librbd performance can keep being close to KRBD.

PS:     Librbd performance are tested both in  fio rbd engine & iscsi (tcmu+librbd).

Thanks.

_______________________________________________

ceph-users mailing list

ceph-users@xxxxxxxxxxxxxx

http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com