Comment 31 for bug 952556

Hi, Just wanted to throw some analysis into this bug report. It's take me ~30+ hours of running tests to gather this data, so apologies if this comes late in the day once the fix has been committed :-/

I've measured Spin Start/Stop counts on a HP Mini netbook measuring the start/stop count during 30 minutes of idle time for various settings of the spindown time. I ran these tests for hdparm -B 127 and also hdparm -B 128, and each test was ran twice to calculate an average and std.deviation. I also used a precision 6 digit multimeter and measured power consumption for each run to measure the impact of the various spindown times.

Attached is an LibreOffice spreadsheet with the data and some graphs.

No big surprises in the data - as the spintime increases we reduce the number of start/stops over the 30 minute idle time and also we see power consumption increasing since we are using more power to keep the drive spinning. The interesting thing to take from the data is the fact that the power savings between 60 seconds spindown time and 600 seconds are ~10-15 mA which is about ~3% of the total power consumption. So probably a good compromise is ~2-3 minutes spindown time for an idle system.

I'd like to repeat this with a more modern laptop and larger HDD, but alas my x220i is away for repair this week.