Now that I am working in a research job again I will be reviving my
blogging. As Software Manager I just did not have time or enough excess
energy. While I am thinking up a list of topics I will start off with a
complaint session. With the new contract I bought a Macbook Pro with
wireless broadband so I could access things like Safari Books Online
without worrying that a net-nanny had decided that programming was bad
language. I am not a mac-o-phile, but when I did the analysis this time
the top of the line Macbook turned out to be the best value for money.
My notebook before that was an IBM running Windows 2000 and then XP.
With 384Mb of RAM I expected a fair bit of hard disk activity. The Mac
has 4Gb, so why does the hard disk run all day? Fortunately "Activity
Monitor" has a disk activity pane. With the system idling I see a write
every 15 to 30 seconds. No reads, as expected. Unfortunately the
monitor did not tell me who was writing to disk. So, for fun (?) I
started killing off tasks one at a time. I hoped to find a culprit. No
such luck. The space apart between right became wider. Once I had
removed most applications it was as long as 4 minutes. I had the drive
wind-down set at 5 minutes and it powered down once. The truth is that
in this modern day of multi-thread programs it makes sense to have
threads running in the background to monitor the context and save it in
case the computer closes down unexpectedly. Or to do housekeeping that
either writes do disk directly or makes changes to the virtual memory
balance. It could be something as simple as a log being updated to say
that no activity has taken place. My gut feeling is that most hard disk
spin most of the time. I wonder how many tons of carbon a day that
equates to for the world's desktops? Or closer to home, how much longer
I can run on battery without the hard disk spinning all the time. I was
going to wait for a solid state drive, but they weren't quite
main-stream. To show that others are thinking on the subject - it is
touted as one of the benefits of hybrid drives. I don't think we need
fancy hardware to improve things today. I don't even think it needs
much of a software change. I think all modern operating systems have
write-behind caches. How about giving me a power saving option that
does something like: if no user activity in 5 minutes if no program
using significant constant amounts of CPU time if write-behind cache is
less than 100Mb (or possibly even 10Mb). if battery power is not low
(notebook or UPS) then Turn off drive and cache writes in memory until
one of the conditions above change. It would have to be a power setting
in the control panel. There are probably some systems out there where
these background tasks are critical and the risk too high. I probably
wouldn't use it on a desktop without a UPS. Given the low cost of a UPS
these days I would probably buy one just to have my hard disk powered
down for a large portion of the day.

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Posted By Paul Marrington to Adept Software Development at 8/27/2007
03:52:00 PM