[NSC-users] Reboot of NSC login nodes and possible performance impact to new jobs

[Mats Kronberg]

Dear NSC users,

This afternoon we will perform an urgent security update of our
clusters Triolith, Gamma, Bi and Elvis.

The update is critical and in our opinion cannot be avoided or postponed.

Unfortunately, the update has a performance impact. A slowdown of
anywhere between 0 to 30% has been reported for various synthetic
benchmarks. However, NSC's estimate is that most HPC applications will
not be significantly affected.

If you find that jobs started after this afternoon run significantly
slower, you can:

- Extend the time limit of already running jobs (using the
"nsc-boost-timelimit" command, or on systems where that is not
available, contact NSC Support (https://www.nsc.liu.se/support/).

- Increase the time limit of new jobs before you submit them (the "-t"
option to sbatch).

If you find HPC applications or job types that are significantly
affected by this update, we would like to hear about it. In this case,
email your findings to support at nsc.liu.se.


All login nodes will be restarted as soon as we're ready to perform
the update. You can expect 10 minutes advance warning via a message
("wall") to logged-in users.

All compute nodes will be updated as soon as the current jobs ends, so
all new jobs will start on updated nodes.


You can find more information about the vulnerability at e.g
https://meltdownattack.com/ and
https://access.redhat.com/security/vulnerabilities/speculativeexecution


-- 
Mats Kronberg, NSC Support <support at nsc.liu.se>