Tag Archives: centos

Things I’ve learned at ISC HPC

I came into the ISC event pretty ignorant. Here’s some of the things I’ve learned.

Supercomputers run Linux. All of them. This isn’t even a topic of discussion. Yes, I’m sure there are some that don’t, but everyone here just assumes that you are running Linux. And probably two or three Apache products.

Supercomputing isn’t about software. This is a hardware conference.

Supercomputing is primarily about how fast you can get rid of heat. And these people are serious about cooling. I’ve seen some amazingly cool cooling rigs. Perhaps the coolest of them was this one: https://youtu.be/hs9WG0ZA79Q  That unit is called the AIC24, and is manufactured by Asperitas, and is a full submersion rack. You lower your blades into oil, which is in turn cooled by a water cooling pump. This is much quieter than fans, and much more efficient. The oil was cool enough to touch. Enormous supercomputing centers are locating on the edge of lakes specifically so that they can pump cool water from the lake into cooling units like this.

I also saw this cool demo: https://youtu.be/aaEQN8DH0kM  You can actually see the oil boiling on the processor. The vapor is then condensed on a cooling unit in the back and trickles back down into the tank.

I have also been blown away by the Student Cluster Competition. These kids have access to hardware that would have blown my mind when I was in school. There’s 11 teams competing on a variety of metrics, and they have these astonishing supercomputers at their disposal. I was also amazed to discover that LINPACK is still one of the standard benchmarks. I used that when I was in college!

The student hardware is all sponsored by the vendors that are here at this event – presumably so that they can benefit from the publicity when they win the contest. Check out some of these rigs:

I was pleasantly pleased to discover that of the 11 teams competing, 8 are running CentOS. One other was running Fedora – they wanted to run CentOS, but needed a newer kernel for something (I wasn’t very clear on what that was. I’ll try to go find out more information today.) The other two were running Ubuntu. CentOS  also appears to be the preferred platform for the various research institutes I’ve talked to. However, these are the groups that chose to come over to the Red Hat booth and talk to me, so I do acknowledge that this is a rather self-selected sample. The sign on the SuSE booth claims that SuSE is the Linux “most used by the top 100 supercomputers.” More research is warranted here. But it appears clear, at least from this small sample, and from conversations with the students, that CentOS is just What You Run when you’re doing supercomputing.

And finally, I’ve learned (not that it’s a big surprise) that one year of high school German, 30 years ago, is not a great deal of help. And that people are amazingly patient and kind with my ignorance – something that I’ve discovered almost everywhere in the world


RDO and CentOS

Continuing in the series about the RDO Meetup in Vancouver, in this recording we have Karsten Wade, of the CentOS project, talking about CentOS’s relationship with RDO, and with OpenStack in general. He talks about the CentOS build infrastructure, CI, package repos, and the CentOS Cloud SIG.

(If the player below doesn’t work for you, you can listen HERE.)


RDO on CentOS 7

With CentOS 7 now available, I quickly put it on my OpenStack demo laptop, and started installing RDO. It mostly just worked, but there were a few roadblocks to circumvent.

As usual, I followed the RDO Quickstart, so I won’t duplicate those steps here, in detail, but it goes like:

sudo yum update -y && sudo yum install -y http://rdo.fedorapeople.org/rdo-release.rpm && sudo yum install -y openstack-packstack && packstack --allinone

Comparison of string with 7 failed

The first problem occurs pretty quickly, in prescript.pp, with the following error message:

Comparison of String with 7 failed

This is due to the change in CentOS versioning scheme – the latest release of CentOS is version 7.0.1406, which is not a number. The script in question assumes that the version number is a number, and does a numerical comparison:

if $::operatingsystem in $el_releases and $::operatingsystemrelease < 7 {

This fails, because $::operatingsystemrelease is a string, not a number.

The solution here is to edit the file /usr/lib/python2.7/site-packages/packstack/puppet/templates/prescript.pp and replace the variable $::operatingsystemrelease with $::operatingsystemmajrelease around line 15.

While you’re at it, do this for every file in that directory, where $operatingsystemrelease is compared to 7.

See https://bugzilla.redhat.com/show_bug.cgi?id=1117035 for more detail, and to track when this is fixed.

mysql vs mariadb

The second problem, I’m not sure I understand just yet. The symptom is that mysql.pp fails with

Error: Could not enable mysqld:

To skip to the end of the story, this appears to be related to the switch from mysql to mariadb about a year ago, finally catching up with CentOS. The related bug is at https://bugzilla.redhat.com/show_bug.cgi?id=981116

The workaround that I used was:

# rm /usr/lib/systemd/system/mysqld.service 
# cp /usr/lib/systemd/system/mariadb.service /usr/lib/systemd/system/mysqld.service
# systemctl stop mariadb
# pkill mysql
# rm -f /var/lib/mysql/mysql.sock

Then run packstack again with the generated answer file from the last time.

However, elsewhere in the thread, we were assured that this shouldn’t be necessary, so YMMV. See https://www.redhat.com/archives/rdo-list/2014-July/msg00055.html for further discussion.

That’s all, folks

After those two workarounds, packstack completed successfully, and I have a working allinone install.

Hope this was helpful to someone.

UPDATE: The next time through, I encountered https://ask.openstack.org/en/question/35705/attempt-of-rdo-aio-install-icehouse-on-centos-7/

The workaround is to replace contents of /etc/redhat-release with “Fedora release 20 (Heisenbug)” and rerun packstack.

Turns out that this also fixes the mysql/mariadb problem above without having to go through the more complicated process.