What you need to know
In the next few weeks quite a few Informatics web servers – and other computing services – will be shut down for a short time. Most of them will go down for only a few minutes, but a few servers will have to be down for an hour or two. The shutdowns will happen one at a time, so we can’t give precise times for each one – but we will do our best to avoid busy periods. Normally we avoid downtime (see “hot migration” below) but on this occasion it’s necessary.
What will be affected?
- Many of the school’s web servers, including those for research groups and institutes
- The RT (issue-tracking) servers which we use for student services and for computing support
- At least one AFS database server (so there will be a few minutes during which there could be slight delays to AFS file access)
- At least one print server
- The new users’ password portal pp.inf.ed.ac.uk
- This server, blog.inf.ed.ac.uk
Informatics computing staff are having a busy summer. There’s lots to do, but in particular we’re working fast to finish the upgrade of the 1250 or so DICE (managed Linux) computers to Ubuntu Linux.
The urgency is because security support for Scientific Linux, our old OS version, will stop later this year. Security updates are a crucial part of protecting our web servers and other computers from botnets, ransomware and other attacks.
We started the upgrade project some years ago, and it’s mostly done – including the lab desktops for instance – but there are still a few hundred computers to go, mostly servers and virtual machines running a variety of services.
We have hundreds of managed virtual machines (VMs). They do various jobs for us. For instance, most of our many websites run on VMs, and so do a lot of infrastructure services (authentication management, automated configuration, printing, all sorts of things).
The VMs are mostly hosted on a few larger servers. From time to time those servers need maintenance, and when that happens, we usually “hot migrate” their VMs to other servers. Hot migration happens transparently – while the VM is moved to another host it appears to keep running without an interruption. That’s very handy. This time though, it’s not possible to hot migrate between an SL7 VM server and an Ubuntu VM server – their virtual hardware support is just too incompatible. Instead, the VMs have to be shut down, then transferred across, reconfigured, then booted up again.
For most VMs this takes just a few minutes. Many of those brief shutdowns won’t be noticed, and in fact most of them have already been done, but a few will be obvious – hence this blog article.
If you have questions, please drop a line to computing support. Thanks.