Hi, I've got almost same problem on my Ultra10 workstation with Debian on it with my an Hitachi Deskstar 250GB.
I succed to make my hdd works, by 1) put the hdd on a Dell PC 2) make it recognise by the bios 3) format it by windows 4) put it back on the Sun Ultra10 5) play a little with fdisk / mkfs Here a part of my logs about dmsg and the drive ... hdb: HDS722525VLAT80, ATA DISK drive hdb: 268435455 sectors (137439 MB) w/7938KiB Cache, CHS=266305/16/63, (U)DMA Hope it's help. Regards. Lorenzo