One of the hazards of going to the pub in Cambridge is that very smart people will occasionally ask you difficult questions. Steve McIntyre, a former Debian Project leader asked our advice as to how Debian should specify a new central build server. Did we think that they’d be best off with lots of RAM or fast SSD, was PCI-E attached SSD better than SATA SSD or even sticking with cheap, slow but very large spinning hard disks.
On the unusual occasions we build software it completes very quickly, and for any big complicated package we’d just install the binary package from Debian. Advice that is almost always spot on, unless you are Debian attempting to make the binary packages in the first place.
We thought about this for a short time and proclaimed confidently that we didn’t know the answer.
However in Mythic Beasts we have a very strong science background. We suggested the right plan was to test it, take a big machine with multiple types of storage, disk, SATA attached SSD and PCI-E flash and try it out. Shortly afterwards our brain kicked in and realised that this looked just like the new VM hosts we were commissioning and with only a slight rearrangement to our plans we could lend one to Debian. Some weeks of work later and the answer is that an SSD makes a huge difference for the working filesystem, otherwise it doesn’t matter.