> Show me a single 15kRPM drive that sustains 90KByte/sec.

Seagate Cheetah 15K.3 in the outer zone.

        57 MBytes/sec to 86 MBytes/sec (depending on the zone)

        http://www.seagate.com/docs/pdf/datasheet/disc/ds_cheetah15k.3.pdf

In general Seagate seems to be pretty truthful with these numbers.
The Barracuda IV I use came within a few percent of Seagate's claimed
speed using dd on the raw device under NetBSD.

-wolfgang
-- 
Wolfgang S. Rupprecht 		     http://www.wsrcc.com/wolfgang/
       The above "From:" address is valid.  Don't mess with it.