Wednesday, July 24, 2013

Server Room and Three Phase Power for Systems Administrators

There doesn't seem to be much educational material about server room power that is comprehensible to systems administrators.  I don't think there is a "typical" sysadmin type out there but I'm guessing that most have had little to no formal training about server room power.  Three phase power may seem like black magic and lots of incorrect assumptions are made, thus I decided to write this post.  Hopefully this will be useful to some sysadmins out there.

Tuesday, July 16, 2013

Per-user /tmp and /dev/shm directories

Updated Oct 7, 2013: Tons of updates
Updated: March 19, 2014: The recommended configuration has been in production for months now and works great

I recently discovered a great feature in Linux that allows for per-process namespaces (aka polyinstantiation).  Different processes on the same machine can have different views of a filesystem, such as where /tmp and /dev/shm are.  You can easily make it so that each user on a shared system has a different /tmp that, to each of them, really looks like (and is) /tmp.  This isn't done by setting an environment variable; this redefines mount points on a per-process basis such that each users' processes are using their own directory as /tmp.

Wednesday, July 10, 2013

Installing a Xeon Phi (MIC) Card in a Dell PowerEdge R720

We got an early release of Dell's Phi installation kit with installation instructions that weren't all that great (to say the least). Dell told me that they are working on better instructions.  In case you're confused, here you go.

A few things to note:
  • We have dual 95W CPUs.  These instructions might be different (correct?) for higher wattage CPUs (larger heat sinks, different plastic baffles?)
  • The extra heat sinks are for the CPUs, not the Phi.  Our 95W CPUs did not need them.
  • The 2.5" and 3.5" mounting brackets are not necessary in our configuration
  • We used a different bracket that was provided
Here are some pictures of what it should look like: