I'll strongly recommend against the use of a Velociraptor (Or any 10000 RPM disk) drive (The heat generated is really great, the ventilation in the PS2's disk drive bay isn't good, and 10000 RPM disks generally don't last as long as any slower disks).
Originally Posted by Clement
The PS2's DVD drive isn't very fast, so you don't need a really fast disk to even beat it (5400 RPM disks will do, but they're quickly disappearing from this world).
SSDs are OK, but they're expensive.
OT: That adaptor looks nice. I wish that I can get one.... but I can't because I don't own a credit card yet.
Unmodified SCPH-77006 with SM 3.6
SCPH-39006 with M-chip modchip, SCPH-10281 NA and refurb Seagate 80GB HDD
SCPH-10000 v1.00 with SCPH-10190 PCMCIA NA and SCPH-20400 HDD unit