Spindles. Old skool administration 101 - when in contention, move to another spindle. Which is why I like my Virtual Machines off my boot drive when possible. On my desktop, believe it or not that 36GB 15k Raptor is still spinning. Half of which is partitioned as swap, the other half, more than adequate speed VM. My laptop has no such luxury, however, and if you've ever tried to run a VM from a thumb drive, you know how to play, "lock up" with the best of us.
Except now the higher-end thumb drives are controlled by an SSD chip, and we have USB 3.0. I've been using both the Sandisk Extreme and the Patriot RAGE to great success, but even those fall short of the glory of the RAGE2: 400MB/sec Read, 300MB/s Write.
All of a sudden I feel like a caveman.