> This is correct, they do have to be the same size.

At the risk of asking a stupid question: has anyone actually *tried* this,
or are we all just reading the "Mirrored Disk/iX" manual to each other?

> using, but I've
> never seen a mirroring solution that didn't require the disc
> drives to be the same size, and for obvious reasons.

My experience with PC-based RAID is exactly the opposite: I've never seen a
mirroring solution that failed if the components of a mirrored pair were
different sizes. Once the mirror is set up, you can't swap in a smaller
drive, but you can always substitute a larger drive. In fact, I *rely* on
this ability, since it allows me to use a single "global spare" drive that
the controller can bring on line to replace any drive in the system that
might fail.

The instructions for the controller explicitly recognize the possibility of
an array composed of dissimilar drives:
 "Group together physical drives that have the same capacity. (If you use
drives with different capacities in an array, all the drives in the array
are treated as though they have the capacity of the smallest drive.)"

and
 "A hot spare must have capacity equal to or greater than the capacity of
the physical drive it would replace."

Oh, yeah, the name of the manual:

"HP NetRAID Series
Installation and Configuration Guide
for HP NetRAID-3Si, HP NetRAID-1Si,
HP NetRAID, and HP NetRAID-1"

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