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 |