Saying Ubuntu doesn't have a place on servers negates your assertion that the OS is a tool and you should use the right tool for the right job. Sometimes you need an OS that updates its kernel more often than basically never. Back when VMs were gaining traction and CentOS 6 was running the 2.6 kernel. That kernel version had zero features that were designed for a virtual deployment. Yes CentOS is incredibly stable and backports all of the security patches, but for VM performance CentOS 6 was outpaced by Ubuntu as a virtual server by a 4x performance increase as a webserver during our testing.
For ceph, it was originally developed solely for Ubuntu and major work into compatibility with CentOS and RHEL didn't start until Redhat purchased ceph. That compatibility took some time and is pretty much fully there now, but back in Firefly and earlier running ceph on centos was a pita.
Back to the point of centos vs Ubuntu... Why limit it there? On the previous mentioned testing I had done with virtual webservers way back when, we had centos responding in 50ms, Ubuntu in 10ms, and a properly configured Gentoo server in 5ms. Please don't be an OS bigot while touting that you should learn the proper tool. Redhat is not the only distribution with a large support structure.
The OS is a tool, but you should actually figure out and use the proper tool for your job. If stability is by far the most important factor, then centos/rhel is likely a great choice for you.
BogdanThanks for the indirect recommendation; we'll ponder on the switch to CentOS, on the medium / long run.Until then, we're looking forward for best practices and advice from the Ceph community, on running the cluster on Ubuntu 16.Regards,_______________________________________________On Sat, Oct 28, 2017 at 2:46 PM, Marc Roos <M.Roos@xxxxxxxxxxxxxxxxx> wrote:
I hope I can post here a general question/comment regarding
distributions. Because I see a lot of stability issues passing by here.
Why are people choosing an ubuntu distribution to run in production?
Mostly I get an answer like they are accustomed to using it. But is the
OS not just a tool? And you have to choose the correct tool for the job
(and then learn to use it)?
When I chose centos it was because it is close related to redhat, and
for critical situations I would choose or switch to the rhel license.
There over 10k people working at redhat to produce a stable os. I am
very pleased with the level of knowledge here and what redhat is doing
general.
I just have to finish with; You people working on Ceph are doing a great
job and are working on a great project!
-----Original Message-----
From: Bogdan SOLGA [mailto:bogdan.solga@xxxxxxxxx]
Sent: vrijdag 27 oktober 2017 18:33
To: ceph-users
Cc: Stephen Oliver; Ákos Nagy
Subject: Kernel version recommendation
Hello, everyone!
We have recently upgraded our Ceph pool to the latest Luminous release.
On one of the servers that we used as Ceph clients we had several freeze
issues, which we empirically linked to the concurrent usage of some I/O
operations - writing in an LXD container (backed by Ceph) while there
was an ongoing PG rebalancing. We searched for the issue's cause through
the logs, but we haven't found anything useful.
At that time the server was running Ubuntu 16 with a 4.5 kernel. We
thought an upgrade to the latest HWE kernel (4.10) would help, but we
had the same freezing issues after the kernel upgrade. Of course, we're
aware that we have tried to fix / avoid the issue without understanding
it's cause.
After seeing the OS recommendations from the Ceph page
<https://github.com/ceph/ceph/blob/master/doc/start/os-recommendations.rst>
, we reinstalled the server (and got the 4.4 kernel), we ran into a
feature set mismatch issue when mounting a RBD image. We concluded
<http://cephnotes.ksperis.com/blog/2014/01/21/feature-set-mismatch-error-on-ceph-kernel-client>
that the feature set requires a kernel > 4.5.
Our question - how would you recommend us to proceed? Shall we
re-upgrade to the HWE kernel (4.10) or to another kernel version? Would
you recommend an alternative solution?
Thank you very much, we're looking forward for your advice.
Kind regards,
Bogdan
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