Posts
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systemd as a CI system
I make fairly extensive use of systemd for scripting tasks which I need to run repeatedly and possibly on schedule (or based on other triggers), and recording a log of the output. At work and among friends, people use Jenkins for the same purpose. This gave me a stupid idea - can I turn systemd into Jenkins, and use it to build Git codebases?
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Dark theme is now live!
This site should now use
prefers-color-schemeto correctly switch to dark mode. Apologies for blinding you -
Advent of Code
So the Advent of Code is running again this year. I’ll be trying to solve each day in Java, Haskell, and Python. All my code will be in this repo and my commentary on the solutions will be in Markdowns in the repo rather than on this site.
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Unraid vs Snapraid
Following on from my previous post, I’ve been experimenting with different setups for storing media on an old computer. The characteristics of this use case is that the files are relatively large, write-once-read-many, do not require high-speed or highly-parallel access, and the disks are a highly heterogenous jumble of spare drives, subject to frequent change. The requirements are just that I have a directory to dump files in, spread them across drives in some manner, and provide protection against up to two disk failures. This makes something like ZFS or Btrfs overkill for my setup, so the two solutions that I looked at were Unraid and a custom SnapRAID + mergerfs setup.
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Bin packing strategies for union mounts
Recently I’ve been configuring an old desktop as a NAS/media centre. I settled on using a “JBOD plus redundancy” system like Unraid or SnapRAID+mergerfs for the flexibility that it provides, as opposed to something more enterprise like FreeNAS/ZFS or a traditional RAID setup.
I intend to write a more thorough comparison of these two solutions in the future, but the short summary relevant to this article is that they use plain old filesystems like XFS on each disk and mount them independently, then provide a writeable union mount view. This isn’t as performant as “real” RAID, but for the scenario of media storage that’s usually not an issue, and in fact has the advantage of only spinning one disk at a time.
Creating a read-only union mount is simple enough, but when you add writeability into the equation you have to decide on a strategy to select a drive to write new files to. In theory this shouldn’t matter, but in practice I want to colocate whole TV shows onto one drive, so that a data loss scenario does not result in me having half of 10 shows rather than 5 complete and 5 completely missing shows. I also wanted to write some code and draw some pretty graphs.