Power, impatience and hibernation.

I did some quick testing of power consumption and boot/shut down times on my Stylistic and found the results interesting. All testing was with a fully charged battery, a fairly stock Ubuntu install, and the tablet was in the mini-dock. Power was measured using a Kill-a-watt at the wall socket, measuring power consumed by the dock/tablet. The results were from the “Watt” mode, not the kwh mode which would be more accurate if using readings for an hour in each mode. I might do that later.

The power consumption in the dock is the same whether the unit is off, hibernated, or suspended: about 1-2 watts. If the unit is on, the hard drive spun up, and the display bright, it uses about 15 watts.

Since power consumption is roughly the same for all suspend/hibernate/power-off, the deciding factor on which to use would be how long it takes to shut down the computer and then how long it takes to recover. Here are the numbers I calculated. Stop times are measured from the point when I clicked shut down/hibernate/suspend i gnome, to the point when the power light either went out (shut down/hibernate) or started blinking (suspend). Starting times are measured from when I hit the power button, to the time when either the GDM log-in screen appeared, or the screen unlock prompt appeared.

Mode Time to stop Time to recover
Power-off 48 seconds 96 seconds
Hibernate 39 seconds 71 seconds
Suspend 11 seconds 13 seconds

Now, this was done with a pretty old hard drive (6.5 GB Toshiba MK6411MAT) which is certainly hurting the boot/hibernate recover times. Also, hibernate brings the system up in a much more useable state (Firefox launched, GNOME all started up, etc) then a cold booted system, but the times were still surprisingly long. Suspend-to-RAM is defintely the way to go if you want the system to be ready in a reasonable amount of time, but has the draw back of requiring power be supplied to the system, even if it is minimal.

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