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DragonFly kernel List (threaded) for 2004-01
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Re: Background fsck

From: David Cuthbert <dacut@xxxxxxxxx>
Date: Mon, 19 Jan 2004 21:51:32 -0500

Matthew Dillon wrote:
    Second, on a modern hard
    drive there isn't all that much of a difference between seeking a few
    tracks and seeking half the disk because it actually takes as long for
    the disk heads to settle on the target track as it does to actually seek
    the heads.

Er, this may or may not be true.

A friend of mine back at Seagate was the servo lead for one of the Cheetah X15 products (LP144? anyway, I've tried my best to drown out the acronyms and silly codes from back then). As I recall, they had it down so that seeks under a certain distance happened much faster than those above this threshold. Other drives (other Seagate models, various competitor models, etc.) would show a roughly constant seek time.

The server drives were always much better than commodity (IDE) drives; they would spend more time tuning those (the build of the parts as well as the servo algorithms).

Take a look at the datasheet for the X15, which quotes both a track-to-track and "average" seek time:


Also note how the commodity drives (80GB Barracuda IDE, in this case) don't:


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