The Register reports large and fast 2.5" HDDs are on the way. According to hardware roadmaps seen at the C-Drive conference, 900GB 2.5" disks spinning at 10,000RPM should become reality in the near future, and those demanding more speed can expect 300GB 2.5" HDDs spinning at 15,000RPM!
The C-Drive conference was told that 900GB 2.5-inch drives spinning at 10,000rpm lay in the relatively near future. A 15K rpm 2.5-inch drive with 300GB capacity is coming too. This would be the fastest small form factor disk drive available. Drive manufacturers have not announced such products.
Compellent currently supplies a 146GB, 3.5-inch STEC solid state drive with Fibre Channel connectivity, and plans to add a 2.5-inch SAS-connected one with a 100GB-plus capacity. Multi-level cell capability would also arrive - STEC coincidentally having 2-bit MLC products available.