[Lustre-discuss] Lustre 2.x support on vanilla kernels

[Andrew Savchenko]

Hello Mark,

On Tue, 5 Jun 2012 17:53:15 -0400 (EDT) Mark Hahn wrote:
> > What bothers me that only RedHat-based systems are claimed to be
> 
> is it safe to assume you know this includes Centos?

Yes, of course. And Scientific Linux too. But currently supported
kernels are RH-5.4-based (for the latest released Lustre 2.0 series).
I doubt Lustre will work without serious changes on RHEL-6.x
versions and related distributions.

> > supported. We will likely use Gentoo on our computing nodes, this
> 
> out of curiosity, why?

There are numerous reasons. In short they are: extreme flexibility
and convenient process of deep updates. And for some applications
performance benefits from careful optimization are really good, but
this reason is secondary.

In more details, I have an experience with binary distributions on
the clusters, mostly RH-based like SLC. While they are easy to
deploy, they are hard in maintenance for our work profile.

We do not have a small, limited number of supported applications, we
need to allow users to use numerous applications, thus we need to
install numerous libraries and packages. Many if not most of them are
absent in the main distribution repository and third-party
repositories are not binary compatible with each other. This creates
a pain, a lot of pain; in the end it is needed to supported own
repository with packaged build from the source code. And where it
comes to building a large amount of packages from the source, Gentoo
rocks, because this is what it were created for.

Also Gentoo is extremely flexible in fine-tuned system configuration,
it is easy to remove unneeded components, which improves security and
simplifies maintenance (you can't do that in binary distributions:
e.g. if program you need links with libABC, requiring daemon ABC to
be running, and you do not need it, you can't just remove it due to
the linking dependencies).

Yet another benefit is a rolling update: it is possible to gradually
update even several years old system without re-installation from
scratch with convenient and half-automated config updates. Of course,
there are ways for a gradual update of a binary distribution, e.g.
RHEL-5.0 to RHEL-6.1, but they are too painful to my taste and often
are not supported by the distribution at all (you're on your own).

There is a drawback of course: it takes longer to perform initial
fine-tuned system setup. As usual, one needs to pay for benefits by
some overhead in other areas.

Of course, you mileage may vary depending on your needs. If you are
happy with your current setup, there are no reasons to change things.

Best regards,
Andrew Savchenko
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