To elaborate on some aspects that have been mentioned already and add
some others::
* Test using iperf3.
* Don't try to use jumbos on networks where you don't have complete
control over every host. This usually includes the main ceph
network. It's just too much grief. You can consider using it for
limited-access networks (e.g. ceph cluster network, hypervisor
migration network, etc) where you know every switch & host is tuned
correctly. (This works even when those nets share a vlan trunk with
non-jumbo vlans - just set the max value on the trunk itself, and
individual values on each vlan.)
* If you are pinging make sure it doesn't fragment otherwise you will
get misleading results: e.g. ping -M do -s 9000 x.x.x.x
* Do not assume that 9000 is the best value. It depends on your NICs,
your switch, kernel/device parameters, etc. Try different values
(using iperf3). As an example the results below are using a small
cheap Mikrotek 10G switch and HPE 10G NICs. It highlights how in
this configuration 9000 is worse than 1500, but that 5139 is optimal
yet 5140 is worst. The same pattern (obviously with different
values) was apparent when multiple tests were run concurrently.
Always test your own network in a controlled manner. And of course
if you introduce anything different later on, test again. With
enterprise-grade kit this might not be so common, but always test if
you fiddle.
MTU Gbps (actual data transfer values using iperf3) - one particular
configuration only
9600 8.91 (max value)
9000 8.91
8000 8.91
7000 8.91
6000 8.91
5500 8.17
5200 7.71
5150 7.64
5140 7.62
5139 9.81 (optimal)
5138 9.81
5137 9.81
5135 9.81
5130 9.81
5120 9.81
5100 9.81
5000 9.81
4000 9.76
3000 9.68
2000 9.28
1500 9.37 (default)
Whether any of this will make a tangible difference for ceph is moot. I
just spend a little time getting the network stack correct as above,
then leave it. That way I know I am probably getting some benefit, and
not doing any harm. If you blindly change things you may well do harm
that can manifest itself in all sorts of ways outside of Ceph. Getting
some test results for this using Ceph will be easy; getting MEANINGFUL
results that way will be hard.
Chris
On 27/05/2020 09:25, Marc Roos wrote:
I would not call a ceph page, a random tuning tip. At least I hope they
are not. NVMe-only with 100Gbit is not really a standard setup. I assume
with such setup you have the luxury to not notice many optimizations.
What I mostly read is that changing to mtu 9000 will allow you to better
saturate the 10Gbit adapter, and I expect this to show on a low end busy
cluster. Don't you have any test results of such a setup?
-----Original Message-----
Subject: Re: Re: [External Email] Re: Ceph Nautius not
working after setting MTU 9000
Don't optimize stuff without benchmarking *before and after*, don't
apply random tuning tipps from the Internet without benchmarking them.
My experience with Jumbo frames: 3% performance. On a NVMe-only setup
with 100 Gbit/s network.
Paul
--
Paul Emmerich
Looking for help with your Ceph cluster? Contact us at https://croit.io
croit GmbH
Freseniusstr. 31h
81247 München
www.croit.io
Tel: +49 89 1896585 90
On Tue, May 26, 2020 at 7:02 PM Marc Roos <M.Roos@xxxxxxxxxxxxxxxxx>
wrote:
Look what I have found!!! :)
https://ceph.com/geen-categorie/ceph-loves-jumbo-frames/
-----Original Message-----
From: Anthony D'Atri [mailto:anthony.datri@xxxxxxxxx]
Sent: maandag 25 mei 2020 22:12
To: Marc Roos
Cc: kdhall; martin.verges; sstkadu; amudhan83; ceph-users; doustar
Subject: Re: Re: [External Email] Re: Ceph Nautius not
working after setting MTU 9000
Quick and easy depends on your network infrastructure. Sometimes
it is
difficult or impossible to retrofit a live cluster without
disruption.
> On May 25, 2020, at 1:03 AM, Marc Roos <M.Roos@xxxxxxxxxxxxxxxxx>
wrote:
>
>
> I am interested. I am always setting mtu to 9000. To be honest I
> cannot imagine there is no optimization since you have less
interrupt
> requests, and you are able x times as much data. Every time there
> something written about optimizing the first thing mention is
changing
> to the mtu 9000. Because it is quick and easy win.
>
>
>
>
> -----Original Message-----
> From: Dave Hall [mailto:kdhall@xxxxxxxxxxxxxx]
> Sent: maandag 25 mei 2020 5:11
> To: Martin Verges; Suresh Rama
> Cc: Amudhan P; Khodayar Doustar; ceph-users
> Subject: Re: [External Email] Re: Ceph Nautius not
> working after setting MTU 9000
>
> 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
>> Chat: https://t.me/MartinVerges
>>
>> croit GmbH, Freseniusstr. 31h, 81247 Munich
>> CEO: Martin Verges - VAT-ID: DE310638492 Com. register:
Amtsgericht
>> Munich HRB 231263
>>
>> Web: https://croit.io
>> YouTube: https://goo.gl/PGE1Bx
>>
>>
>>> 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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