[ceph-users] Librbd performance VS KRBD performance

[赵赵贺东]

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.

[Gregory Farnum]

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...

Post by 赵赵贺东
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.
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
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

[赵赵贺东]

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!

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

[Jason Dillaman]

Attempting to send 256 concurrent 4MiB writes via librbd will pretty
quickly hit the default "objecter_inflight_op_bytes = 100 MiB" limit,
which will drastically slow (stall) librados. I would recommend
re-testing librbd w/ a much higher throttle override.

Post by 赵赵贺东
Thank you for your attention.
Our test are in run in physical machine environments.
[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.
[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
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
create_timestamp: Wed Nov 14 09:21:18 2018
* data_pool is a EC pool
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!
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...

Post by 赵赵贺东
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.
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
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

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

[赵赵贺东]

Thanks you for your suggestion.
It really give me a lot of inspirations.


I will test as your suggestion, and browse through src/common/config_opts.h to see if I can find some configs performance related.

But, our osd nodes hardware itself is very poor, that is the truth…we have to face it.
Two osds in an arm board, two gb memory and 2*10T hdd disk on board, so one osd has 1gb memory to support 10TB hdd disk, we must try to make cluster works better as we can.


Thanks.

Post by Jason Dillaman
Attempting to send 256 concurrent 4MiB writes via librbd will pretty
quickly hit the default "objecter_inflight_op_bytes = 100 MiB" limit,
which will drastically slow (stall) librados. I would recommend
re-testing librbd w/ a much higher throttle override.

Post by 赵赵贺东
Thank you for your attention.
Our test are in run in physical machine environments.
[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.
[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
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
create_timestamp: Wed Nov 14 09:21:18 2018
* data_pool is a EC pool
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!
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...

Post by 赵赵贺东
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.
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
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

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

--
Jason

[赵赵贺东]

I test in 12 osds cluster, change objecter_inflight_op_bytes from 100MB to 300MB, performance seems not change obviously.
But at the beginning , librbd works in better performance in 12 osds cluster. So it seems meaning less for me.

Post by 赵赵贺东

Post by Jason Dillaman

Post by 赵赵贺东

Post by 赵赵贺东
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).

Our problem is librbd bad performance in big cluster (72 osds)
But I can not test in 72 osds right now, some other tests are running .
I will test in 72 osds when our cluster is ready.

It is a little hard to understand that objecter_inflight_op_bytes=100MB works well in 12 osds cluster, but works poor in 72 osd clusters.
Dose objecter_inflight_op_bytes not have an effect on krbd, only effect librbd?

Thanks.

Post by 赵赵贺东
Thanks you for your suggestion.
It really give me a lot of inspirations.
I will test as your suggestion, and browse through src/common/config_opts.h to see if I can find some configs performance related.
But, our osd nodes hardware itself is very poor, that is the truth…we have to face it.
Two osds in an arm board, two gb memory and 2*10T hdd disk on board, so one osd has 1gb memory to support 10TB hdd disk, we must try to make cluster works better as we can.
Thanks.

Post by Jason Dillaman
Attempting to send 256 concurrent 4MiB writes via librbd will pretty
quickly hit the default "objecter_inflight_op_bytes = 100 MiB" limit,
which will drastically slow (stall) librados. I would recommend
re-testing librbd w/ a much higher throttle override.

Post by 赵赵贺东
Thank you for your attention.
Our test are in run in physical machine environments.
[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.
[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
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
create_timestamp: Wed Nov 14 09:21:18 2018
* data_pool is a EC pool
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!
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...

Post by 赵赵贺东
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.
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
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

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

--
Jason

[Jason Dillaman]

Post by 赵赵贺东
I test in 12 osds cluster, change objecter_inflight_op_bytes from 100MB to 300MB, performance seems not change obviously.
But at the beginning , librbd works in better performance in 12 osds cluster. So it seems meaning less for me.

Post by 赵赵贺东

Post by Jason Dillaman

Post by 赵赵贺东

Post by 赵赵贺东
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).

Our problem is librbd bad performance in big cluster (72 osds)
But I can not test in 72 osds right now, some other tests are running .
I will test in 72 osds when our cluster is ready.
It is a little hard to understand that objecter_inflight_op_bytes=100MB works well in 12 osds cluster, but works poor in 72 osd clusters.
Dose objecter_inflight_op_bytes not have an effect on krbd, only effect librbd?

Correct -- the "ceph.conf" config settings are for user-space tooling
only. Given the fact that you are writing full 4MiB objects in your
test, any user-space performance degradation is probably going to be
in the librados layer and below. That 100 MiB limit setting will block
the IO path while it waits for in-flight IO to complete. You also
might be just hitting the default throughput of the lower-level
messenger code, so perhaps you need to throw more threads at it
(ms_async_op_threads / ms_async_max_op_threads) or change its
throttles (ms_dispatch_throttle_bytes). Also, depending on your
cluster and krbd versions, perhaps the OSDs are telling your clients
to back-off but only librados is responding to it. You should also
take into account the validity of your test case -- does it really
match your expected workload that you are trying to optimize against?

Post by 赵赵贺东
Thanks.

Post by 赵赵贺东
Thanks you for your suggestion.
It really give me a lot of inspirations.
I will test as your suggestion, and browse through src/common/config_opts.h to see if I can find some configs performance related.
But, our osd nodes hardware itself is very poor, that is the truth…we have to face it.
Two osds in an arm board, two gb memory and 2*10T hdd disk on board, so one osd has 1gb memory to support 10TB hdd disk, we must try to make cluster works better as we can.
Thanks.

Post by Jason Dillaman
Attempting to send 256 concurrent 4MiB writes via librbd will pretty
quickly hit the default "objecter_inflight_op_bytes = 100 MiB" limit,
which will drastically slow (stall) librados. I would recommend
re-testing librbd w/ a much higher throttle override.

Post by 赵赵贺东
Thank you for your attention.
Our test are in run in physical machine environments.
[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.
[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
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
create_timestamp: Wed Nov 14 09:21:18 2018
* data_pool is a EC pool
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!
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...

Post by 赵赵贺东
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.
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
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

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

--
Jason

[赵赵贺东]

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