The perks of being a VM

Several of the CS department’s servers are virtual machines. While running VM’s adds complexity, it also lets you do things like octuple* system RAM in five minutes from your laptop.

For context, Earlham CS runs a Jupyterhub server for the first- and second-semester CS students. We want to provide a programming environment (in this case Python, a terminal, and a few other languages) so students can focus on programming instead of administration, environment, etc. Jupyter is handy for that purpose.

The issue: Each notebook takes a relatively large amount of RAM. There are 60 or so intro CS students here. The Xen virtual machine hosting Jupyter was simply not equipped for that load. So at the request of my colleagues teaching the course, I visited a lab today. After observing the problem, we took five minutes to shut the server down, destroy the volume, change a single number in a single config file, and bring it all back to life with a boosted configuration. We’ve had no additional problems – so far. 🙂

Running a VM is frequently more complex than running on bare hardware. But the alternative is this:

I wish I had some of the “upcoming maintenance” email notifications we sent out in my ECCS sysadmin days for comparison. They were basically “no email, no websites for several days while we rebuild this server from parts, mmmkay?”


Because we do so much of our administration in software, we’ve mostly avoided that problem in recent years. The closest we’ve gotten to scrambling hardware lately was recovering from disk failures after a power outage over the summer. We had to send a lot of “sorry, X is down” emails. I wouldn’t want that to be our approach to managing all servers all the time.

(Of course there are many other alternatives, but running Xen VM’s serves our purposes nicely. It’s also, for many reasons, good practice for our student system administrators.)

*I tweeted about this originally and said we quadrupled the RAM. In fact, a previously-arranged RAM doubling had been specified in the VM’s config file but not implemented. Before we restarted the machine, we decided to boost it even more. Ultimately we quadrupled the double of the previous RAM amount.

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