Archive for August, 2014

I/O performance of self-built low-power Linux home NAS

Friday, August 29th, 2014

So, my article about building a low power Linux home NAS got quite a lot of attention, and several commenters wanted information about the performance.

I/O performance was something that I was curious about it when I built it, especially if using encrypted disks (LUKS) with such a low-power machine, so I did some very basic tests and the results are below. All tests are done with a large (3.5GB) file/data, intentionally larger than the memory. They involve writing to an ext4 filesystem (default configuration with RHEL6) sitting over a RAID0 MD array. Disks are 2 x Seagate SpinPoint M8/ST1000LM024 1TB 2.5″.

I’ve got to emphasise that these are quick and dirty initial results to give an idea; I’ve not analysed them deeply and there might be methodological flaws (e.g. I didn’t force caching off)

Sequential read/write (dd)

Non-encrypted Encrypted (LUKS)
Block size (bytes) Read (MB/s) Write (MB/s) Read (MB/s) Write (MB/s)
4096 43.9 21.7 1.4 11.1
8192 52.7 38.2 20.3 15.3
65536 51.6 45.0 26.5 21.1
131072 51.1 45.5 27.1 22.0