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: w...@globe.de [mailto:w...@globe.de]
Sent: 21 July 2016 13:23
To: n...@fisk.me.uk; 'Horace Ng' <hor...@hkisl.net>
Cc: ceph-users@lists.ceph.com
Subject: Re: [ceph-users] 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-boun...@lists.ceph.com] On Behalf
Of w...@globe.de
Sent: 21 July 2016 13:04
To: n...@fisk.me.uk; 'Horace Ng' <hor...@hkisl.net>
Cc: ceph-users@lists.ceph.com
Subject: Re: [ceph-users] 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-boun...@lists.ceph.com] On
Behalf Of Horace
Sent: 21 July 2016 10:26
To: w...@globe.de
Cc: ceph-users@lists.ceph.com
Subject: Re: [ceph-users] 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: w...@globe.de
To: ceph-users@lists.ceph.com
Sent: Thursday, July 21, 2016 5:11:21 PM
Subject: [ceph-users] 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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