All,
Regarding Martin's observations about Jumbo Frames....
I have recently been gathering some notes from various internet sources
regarding Linux network performance, and Linux performance in general,
to be applied to a Ceph cluster I manage but also to the rest of the
Linux server farm I'm responsible for.
In short, enabling Jumbo Frames without also tuning a number of other
kernel and NIC attributes will not provide the performance increases
we'd like to see. I have not yet had a chance to go through the rest of
the testing I'd like to do, but I can confirm (via iperf3) that only
enabling Jumbo Frames didn't make a significant difference.
Some of the other attributes I'm referring to are incoming and outgoing
buffer sizes at the NIC, IP, and TCP levels, interrupt coalescing, NIC
offload functions that should or shouldn't be turned on, packet queuing
disciplines (tc), the best choice of TCP slow-start algorithms, and
other TCP features and attributes.
The most off-beat item I saw was something about adding IPTABLES rules
to bypass CONNTRACK table lookups.
In order to do anything meaningful to assess the effect of all of these
settings I'd like to figure out how to set them all via Ansible - so
more to learn before I can give opinions.
--> If anybody has added this type of configuration to Ceph Ansible,
I'd be glad for some pointers.
I have started to compile a document containing my notes. It's rough,
but I'd be glad to share if anybody is interested.
-Dave
Dave Hall
Binghamton University
On 5/24/2020 12:29 PM, Martin Verges wrote:
Just save yourself the trouble. You won't have any real benefit from MTU
9000. It has some smallish, but it is not worth the effort, problems, and
loss of reliability for most environments.
Try it yourself and do some benchmarks, especially with your regular
workload on the cluster (not the maximum peak performance), then drop the
MTU to default ;).
Please if anyone has other real world benchmarks showing huge differences
in regular Ceph clusters, please feel free to post it here.
--
Martin Verges
Managing director
Mobile: +49 174 9335695
E-Mail: martin.verges@xxxxxxxx
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Am So., 24. Mai 2020 um 15:54 Uhr schrieb Suresh Rama <sstkadu@xxxxxxxxx>:
Ping with 9000 MTU won't get response as I said and it should be 8972. Glad
it is working but you should know what happened to avoid this issue later.
On Sun, May 24, 2020, 3:04 AM Amudhan P <amudhan83@xxxxxxxxx> wrote:
No, ping with MTU size 9000 didn't work.
On Sun, May 24, 2020 at 12:26 PM Khodayar Doustar <doustar@xxxxxxxxxxxx>
wrote:
Does your ping work or not?
On Sun, May 24, 2020 at 6:53 AM Amudhan P <amudhan83@xxxxxxxxx> wrote:
Yes, I have set setting on the switch side also.
On Sat 23 May, 2020, 6:47 PM Khodayar Doustar, <doustar@xxxxxxxxxxxx>
wrote:
Problem should be with network. When you change MTU it should be
changed
all over the network, any single hup on your network should speak and
accept 9000 MTU packets. you can check it on your hosts with
"ifconfig"
command and there is also equivalent commands for other
network/security
devices.
If you have just one node which it not correctly configured for MTU
9000
it wouldn't work.
On Sat, May 23, 2020 at 2:30 PM sinan@xxxxxxxx <sinan@xxxxxxxx>
wrote:
Can the servers/nodes ping eachother using large packet sizes? I
guess
not.
Sinan Polat
Op 23 mei 2020 om 14:21 heeft Amudhan P <amudhan83@xxxxxxxxx> het
volgende geschreven:
In OSD logs "heartbeat_check: no reply from OSD"
On Sat, May 23, 2020 at 5:44 PM Amudhan P <amudhan83@xxxxxxxxx>
wrote:
Hi,
I have set Network switch with MTU size 9000 and also in my
netplan
configuration.
What else needs to be checked?
On Sat, May 23, 2020 at 3:39 PM Wido den Hollander <
wido@xxxxxxxx
wrote:
On 5/23/20 12:02 PM, Amudhan P wrote:
Hi,
I am using ceph Nautilus in Ubuntu 18.04 working fine wit MTU
size
1500
(default) recently i tried to update MTU size to 9000.
After setting Jumbo frame running ceph -s is timing out.
Ceph can run just fine with an MTU of 9000. But there is
probably
something else wrong on the network which is causing this.
Check the Jumbo Frames settings on all the switches as well to
make
sure
they forward all the packets.
This is definitely not a Ceph issue.
Wido
regards
Amudhan P
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