[Beowulf] cluster os

Andrew M.A. Cater amacater at galactic.demon.co.uk
Fri May 20 13:40:50 PDT 2016

On Fri, May 20, 2016 at 09:42:25AM +1000, Christopher Samuel wrote:
> On 19/05/16 20:44, Jörg Saßmannshausen wrote:
> > The upgrade in Debian is working really well. You really can
> > install a machine once and then you can upgrade it to the latest
> > OS without much issues. [...]
> Agreed, Debian is great for this (which is why we're running it on our
> infrastructure boxes).  It also doesn't tend to break things on point
> releases, unlike Red Hat.

Point releases work fine in Debian because of three things: testing, packaging
policy and relative frequency. RHEL only produces point releases every ten months 
or so such that each update is quite large.

> > This experience seems to be in stark difference from the OS upgrade on the 
> > central cluster (RedHat) where the cluster needed to be installed from 
> > scratch. At least that was my understanding. 
> That's certainly true up to RHEL6, there is some ability to upgrade from
> RHEL6 to RHEL7 now though (never tried it).

It doesn't work well: for anybody running CentOS - which is binary compatible -
this is not supported at all. The script was not recommended unless you had
RHEL support on hand. RHEL and CentOS 7 are very significantly different in
init scripts, firewall config etc from 6.* 

Plan upgrades very carefully.

> We're tied to RHEL due to hardware vendor support requirements. :-/

This is the sort of thing that gets you: mass storage, high performance 
interconnects and so on are often only supported by drivers for Red Hat
base OS versions, sometimes even tied to specific kernel versions.

My beef with the RHEL ecosystem - as distinct from Debian - is that so
much has to be pulled from third party repositories like EPEL, elrepo and
so on where there is no guarantee whatever as to code quality. In this,
however, I'm a zealot - and I don't run a cluster or advise on OS choices
at the moment.

> All the best,
> Chris

As also to all readers and contributors on this list - which _still_ has
the highest signal-noise of any infromation I read.


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