Comment 757 for bug 59695

Reducing the frequency of unparking is nearly impossible in Ubuntu, at least for the developers atm.
It isn't enough to higher the DIRTY_RATIO like laptop-mode does or exit or disabling hal-polling. If apps like Firefox are used they poll very often.
I personally got longer sleep times (nearly a minute) after doing the mentioned and moving /tmp and the firefox profile, macromedia and java directory to tmpfs. The problem is that the directories have to be synced to disk before shutdown and there are several more apps that poll recently I guess.

I still think it is the best to poll affected hard drives (high SMART parking values) recently and don't change the apm value. Of course this only makes sense if the hard drives doesn't get as hot with polling as with disabled apm.

At least for laptops the problem might be gone soon when SSDs are used more recently so just waiting might solve the issue too ;) .