What are the best practices for disk spindown on a Netbook running on Ubuntu 10.04?

I have a Netbook (Samsung N210) running Ubuntu 10.04 Netbook Edition. Generally, I'm very happy with it. However, I'm not getting quite as much battery life out of it as I expected based on the manufacturer's claims (and from what I have read elsewhere) - perhaps 4-5 hours, even when doing simple text editing etc.

I tried installing the laptop-mode-tools package, which seemed extremely disk spindown happy - the disk spun up and down a lot - maybe every 5 seconds. I know laptop disks are designed for frequent spindowns, but that made me nervous and I uninstalled it. The alternative seems to be the default package pm-utils-powersave-policy, but that seems to almost never spin down.

Incidentally, I have the checkbox "Spin down hard disks when possible" checked in my Power Management Preferences, but I'm not clear what that affects or interacts with - it would be interesting to know.

So: what should I do? I'd like to eke out a bit more battery life, but the laptop-mode-tools settings seem extremely aggressive out-of-the-box. I know they can be tuned, but there seems to be a huge number of them - I'd prefer something more out-of-the-box and tested.

Answer

Most laptop-mode settings won't cause any harm. Parameter choice is a compromise between power consumption and performance — a fairly personal choice, so it's expected that you'll want to tune the settings.

The noflushd package can make your disk spin down for longer periods of time by delaying writes (at the expense of data loss if your system crashes or runs out of battery before the delayed writes actually occur).

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The hard disk only contributes a small part of your laptop's power consumption. Noise reduction, not power saving, is the primary reason to spin the disk down. See e.g. Who Eats the Energy? Power Consumption on a Modern Laptop — it's a bit dated, but I think the approximate results still hold.

Reduce the brightness of the display as far as you can go.

Turn off the wifi if you're not using it.

Try running powertop to find programs that are running in the background and prevent the CPU from switching to a low-power state.