The effects of Acoustic Management on rotational media disks.

So one of the trends I’ve been seeing in WDRAPs I’ve performed is that companies are making use of older hardware for newer tasks on a much more frequent basis than before.  Budgets seem to mandate a 4-5 year (or longer) pc recycle timeframe and the net result of this is companies are running their new image of Windows 7 on hardware that in some cases is over 7 years old (personal experience talking here, no statistics to back it up sorry, though that might be interesting).

So when I go into a company to do a WDRAP I am often evaluating the security and performance of an older chassis.  Something I’m frequently running into is that some models of desktop have Automatic Acoustic Management (AAM) enabled by default to a value of 128 (quiet).  Sometimes, the BIOS is actually set to ‘Bypass’ which at first blush might make the user or administrator think the BIOS has this feature disabled.  Incorrect in my experience!  Bypass actually seems to let the disk decide, so if the manufacturer of a disk set the disk to prefer quiet mode, Bypass will let the disk run at a slower rotational speed to keep the head quiet.

This increases the seek time noticeably, as well as overall transfer time.  (You can go over more blocks in a minute if you are spinning at 7200 RPMs than if you are spinning at say, 5400 RPM, same goes here for AAM).

Setting the BIOS to Performance (forcing the drive to run at the 254 level of performance instead of 128/quiet) has caused some boot times of older XP images to speed up by over 100 seconds in the field.

So really, check out this setting.  You might also note that some hardware vendors in later/modern disables this setting and sells it as a performance gain, rightfully so.  Most drives are fairly quiet these days anyway, so much so that most models of hardware I’ve changed this on the end user doesn’t notice the difference in noise levels, only performance.

Of course your mileage will vary by model of drive, motherboard, and BIOS.

Additional links that you might find interesting on the topic are listed here.