Do the differences affect long term reliability?

[Hugger]

I got some good advice
about a week ago about using an external hard drive
as part of my back up system.
My question is a simple one.
Which holds up better. A 2.5 7200 rpm or a 3.5 7200 rpm hard drive?
Whichever I get will be used with a Windows 7 x64 laptop.
Thanks for any help.
Hugger

[Keatah]

Well, I've had more big disks fail on me than I've had small disks fail, if that means anything.

A 2.5 drive may be more resistant to shock and jostling about, it is, after all, engineered for the mobile market. There's less mass to bounce around and components are lighter. 2.5 drive electronics seem to be more reliable compared to 3.5 form factor electronics. Smaller electronics tend to have less thermal expansion. And the HDD metal housing of a big disk expands and contracts more with temperature change, thereby pulling on itself and electronics and controller board.

A 2.5 drive will tend to fail more catastrophically compared to a bigger disk, and data recovery could also be more difficult. But since we're "in the business" of backing up we won't need the services of Drivesavers or OnTrack, now will we?

As for persistence of "magnetic bits" on the surfaces, there's lots of factors. Bigger disks tend to have larger domains and are more "stronger" and permanent. And know that the bits aren't really bits, but bouncy analog waves that look like this:
ø,¸¸,ø¤º°`°º¤ø,¸¸,ø¤º°¤ø,¸¸,ø¤º°`°º¤ø,¸¸,ø¤º°
!¸.•*´¯)¸,ø¤º°`°º¤ø,¸¸,¸,ø•*´¯)!¸.•*´¯)¸,ø¤º°`°º¤ø,¸¸,¸,ø•*´¯)
.¸.•*´¯)¸.•*´¯)¸..¸.•*´¯)¸.•*´¯)¸..¸.•*´¯)¸.•*´¯)¸.
(¯`'•.¸(¯`'•.¸(¯`'•.¸_¸.•'´¯)¸.•'´¯)¸.•'´¯)
°°°¤(¯`'•.¸*¨¨*:•.•:*¨¨**¨¨*:•.•:*¨¨*:• ¸.•'´¯)¤°°°

Not like this:
111011001010101111101010100101001011
110101010101111010000101010111000101

Ain't that just -:¦:- FABULOUS -:¦:-

To use an overused corporate buzzphrase "at the end of the day" I'd go with a smaller disk and if you're concerned about longevity and persistence, just rewrite the data. ALL HAIL 2.5 DRIVES! WHEEE!!!