disk "shrunk" after going into a 2850

[RB]

This is typical of RAID environments, and expected behavior.  If a
drive is physically removed from an array and later replaced by
another without removing, resizing, or otherwise modifying the array
to make it unaware of that channel/slot, it is expected to treat
subsequent drives as replacements and automatically perform the
necessary sizing/copy/parity operations.  This is so engineers can
tell raised-floor goons "go pull the drive with the orange light
blinking on it and replace it with this one" at 02:00 with little or
no "intelligent" intervention needed.

I don't know what RAID controllers you've had, but across many dozens
of Dell, IBM, and HP 'enterprise' servers that is the SOP I've seen
when physically replacing drives.  A RAID controller is no more aware
of what constitutes 'valid' data than your lungs do 'valid' air - they
move and exchange bits [gases] in a very standard, repeatable fashion.
 That's it.

Every poweredge purchase is accompanied with an offer of the
applicable RAID controller's documentation, either on optical media
(free) or printed (nominal charge).  If you did not purchase your
system new and did not receive that documentation, it was rather
unwise to leap headlong into disaster testing with data you couldn't
afford to lose.  The obvious starting place to look for such
documentation is the big blue question-mark "Support" link on Dell's
front page - 8 clicks later
(http://support.dell.com/support/edocs/systems/pe2850/en/index.htm) I
find a listing of some very pertinent documentation.

RB