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What i not really undertand is:
Lets say the Intel P3700 works with 200 MByte/s rados bench one
thread... See Nicks results below...
If we have multiple OSD Nodes. For example 10 Nodes.
Every Node has exactly 1x P3700 NVMe built in.
Why is the single Thread performance exactly at 200 MByte/s on
the rbd client with 10 OSD Node Cluster???
I think it must be at 10 Nodes * 200 MByte/s = 2000 MByte/s.
Everyone look yourself at your cluster.
dstat -D sdb,sdc,sdd,sdX ....
You will see that Ceph stripes the data over all OSD's in the
cluster if you test at the client side with rados bench...
rados bench -p rbd 60 write -b 4M -t 1
Is there not a way to enable Linux page Cache? So do
not user D_Sync...
Then we would the dramatically performance improve.
Am 21.07.16 um 14:33 schrieb Nick Fisk:
-----Original Message-----
From: wr@xxxxxxxx [mailto:wr@xxxxxxxx]
Sent: 21 July 2016 13:23
To: nick@xxxxxxxxxx; 'Horace Ng' <horace@xxxxxxxxx>
Cc: ceph-users@xxxxxxxxxxxxxx
Subject: Re: Ceph + VMware + Single Thread
Performance
Okay and what is your plan now to speed up ?
Now I have come up with a lower latency hardware design, there
is not much further improvement until persistent RBD caching is
implemented, as you will be moving the SSD/NVME closer to the
client. But I'm happy with what I can achieve at the moment. You
could also experiment with bcache on the RBD.
Would it help to put in multiple P3700
per OSD Node to improve performance for a single Thread
(example Storage VMotion) ?
Most likely not, it's all the other parts of the puzzle which
are causing the latency. ESXi was designed for storage arrays
that service IO's in 100us-1ms range, Ceph is probably about 10x
slower than this, hence the problem. Disable the BBWC on a RAID
controller or SAN and you will the same behaviour.
Regards
Am 21.07.16 um 14:17 schrieb Nick Fisk:
-----Original Message-----
From: ceph-users
[mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf
Of wr@xxxxxxxx
Sent: 21 July 2016 13:04
To: nick@xxxxxxxxxx; 'Horace Ng' <horace@xxxxxxxxx>
Cc: ceph-users@xxxxxxxxxxxxxx
Subject: Re: Ceph + VMware + Single Thread
Performance
Hi,
hmm i think 200 MByte/s is really bad. Is your Cluster in
production right now?
It's just been built, not running yet.
So if you start a storage migration
you get only 200 MByte/s right?
I wish. My current cluster (not this new one) would storage
migrate at
~10-15MB/s. Serial latency is the problem, without being
able to
buffer, ESXi waits on an ack for each IO before sending the
next. Also it submits the migrations in 64kb chunks, unless
you get VAAI
working. I think esxi will try and do them in parallel, which
will help as well.
I think it would be awesome if you
get 1000 MByte/s
Where is the Bottleneck?
Latency serialisation, without a buffer, you can't drive the
devices
to 100%. With buffered IO (or high queue depths) I can max
out the journals.
A FIO Test from Sebastien Han give
us 400 MByte/s raw performance from the P3700.
https://www.sebastien-han.fr/blog/2014/10/10/ceph-how-to-test-if-your
-ssd-is-suitable-as-a-journal-device/
How could it be that the rbd client performance is 50%
slower?
Regards
Am 21.07.16 um 12:15 schrieb Nick Fisk:
I've had a lot of pain with this,
smaller block sizes are even worse.
You want to try and minimize latency at every point as
there is no
buffering happening in the iSCSI stack. This means:-
1. Fast journals (NVME or NVRAM)
2. 10GB or better networking
3. Fast CPU's (Ghz)
4. Fix CPU c-state's to C1
5. Fix CPU's Freq to max
Also I can't be sure, but I think there is a metadata
update
happening with VMFS, particularly if you are using thin
VMDK's, this
can also be a major bottleneck. For my use case, I've
switched over to NFS as it has given much more
performance at scale and
less headache.
For the RADOS Run, here you go
(400GB P3700):
Total time run: 60.026491
Total writes made: 3104
Write size: 4194304
Object size: 4194304
Bandwidth (MB/sec): 206.842
Stddev Bandwidth: 8.10412
Max bandwidth (MB/sec): 224
Min bandwidth (MB/sec): 180
Average IOPS: 51
Stddev IOPS: 2
Max IOPS: 56
Min IOPS: 45
Average Latency(s): 0.0193366
Stddev Latency(s): 0.00148039
Max latency(s): 0.0377946
Min latency(s): 0.015909
Nick
-----Original Message-----
From: ceph-users
[mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On
Behalf Of Horace
Sent: 21 July 2016 10:26
To: wr@xxxxxxxx
Cc: ceph-users@xxxxxxxxxxxxxx
Subject: Re: Ceph + VMware + Single
Thread Performance
Hi,
Same here, I've read some blog saying that vmware will
frequently
verify the locking on VMFS over iSCSI, hence it will
have much slower performance than NFS (with different
locking mechanism).
Regards,
Horace Ng
----- Original Message -----
From: wr@xxxxxxxx
To: ceph-users@xxxxxxxxxxxxxx
Sent: Thursday, July 21, 2016 5:11:21 PM
Subject: Ceph + VMware + Single Thread
Performance
Hi everyone,
we see at our cluster relatively slow Single Thread
Performance on the iscsi Nodes.
Our setup:
3 Racks:
18x Data Nodes, 3 Mon Nodes, 3 iscsi Gateway Nodes
with tgt (rbd cache off).
2x Samsung SM863 Enterprise SSD for Journal (3 OSD per
SSD) and 6x
WD Red 1TB per Data Node as OSD.
Replication = 3
chooseleaf = 3 type Rack in the crush map
We get only ca. 90 MByte/s on the iscsi Gateway
Servers with:
rados bench -p rbd 60 write -b 4M -t 1
If we test with:
rados bench -p rbd 60 write -b 4M -t 32
we get ca. 600 - 700 MByte/s
We plan to replace the Samsung SSD with Intel DC P3700
PCIe NVM'e
for the Journal to get better Single Thread
Performance.
Is anyone of you out there who has an Intel P3700 for
Journal an
can give me back test results with:
rados bench -p rbd 60 write -b 4M -t 1
Thank you very much !!
Kind Regards !!
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