Comments posted earlier about the slower hard drives on laptops were pretty brief, so a little more might be helpful.

Most early desktop hard drives had a "Park" position for the read/write heads so that there was a place to put them where they couldn't crash into the data surfaces when you moved the machine. With very early drives, you had to execute a "Park Heads" command before turning the machine off, if you didn't want to risk damage when the machine was moved. In some of these drives, the heads actually were locked in place by a mechanical latch or detent when you parked them.

Slightly more recent desktop drives incorporated an "autopark" so that any time the power to the drive was off, the heads were moved to a position where they could only hit a "dead track" at one end or the other of the disk if the drive was "shaken or stirred." Sometimes the "autopark" position was fairly securely "detented" and other times not.

"Modern" desktop drives usually move the heads to one end of the disk during shutdown, and usually hold them there with reasonable security; but with newer read/write head design and better magnetic coatings the risk of damage to the data area is very low for the kinds of bumps and bangs expected for desktop machines.

Since laptops may be jostled around quite a bit even when the drive is running, and may experience very large shocks during transport, it remains necessary to remove the heads from the data area any time they're not actually performing a read/write operation. Because of the higher shock levels that are expected, when the heads are "parked" they must be fairly firmly restrained.

Specifications for hard drives may (rarely) show an "initial data acquisition time" or "initial seek time" which is the time required for the heads to move from the "parked" position to any place on the disk and to read a cluster. This is invariably an interminably long time – on the order of 4 to 20 times the "read time." (time is a relative thing)

The "read time" (various terms may be used – "seek time" and "data acquisiton time" are others) is the time required for the heads to move from one cluster in the data area to another cluster, and read the new cluster into RAM. Read time numbers are very closely comparable for desktop and laptop drives, and are the only thing commonly reported on the box for either.

On a desktop, it's okay for the head to just sort of "loiter" wherever it happens to be, so the next request for it to read or write something can be quickly executed. Since the laptop may be jostled about at any time, the head may "loiter" briefly, but anytime there's a significant pause in the read/write requests, it MUST GO TO A SAFE PLACE – i.e. it goes and parks.

A laptop drive may be nearly as "fast" as a desktop drive for reading a single file into RAM, but in a very large percentage of the "reads" it will need to come from the parking spot for each "continous read." Given that a simple operation like opening Word with no document in it may require opening and closing nearly 1,000 separate files, it is pretty easy to see that even a few "parks" while all this happens is going to make the laptop drive look pretty slow, since each "return from park" takes as long as reading 10 or so clusters.

A normal destop hard drive likely would not survive long in laptop use, since it lacks the "physical security feature" of parking the heads where they can tolerate being moved. Those of use who use "external drives" of common kinds to transport data from one place to another do assume a significant risk, since these drives are not meant to be moved around. It is absolutely imperative that an "external desktop" drive of this sort must be allowed to come to a FULL STOP before being moved at all, and then must be handled carefully when being carried about. The packing it came in, or a close equivalent, should be used where possible anytime one is being moved.

"Transportable" external hard drives are available, generally at about 4X (?) the cost of "desktop external" ones, for those who really want something "portable." These kinds of hard drives should incorporate the same "head park" and other shock tolerant design features as in laptop drives.

John