Sun blogger Anatol Studler makes that case in a recent blog that you should avoid placing SSDs in traditional arrays.

A traditional array has a controller with a certain fixed amount of compute power and I/O capability. Placing fast SSDs into an array designed for traditional disks is, "is quite surprising to me, as it is comparable to place a 8-cylinder bi-turbo engine with 450HP into an entry level car."

Anatol continues, "Traditional midrange arrays are developed to handle hundreds of traditional (15k RPM) harddisk drives. A traditional harddisk is capable of running about 250 IO/s. Now if we compare this with the actual enterprise class Solid State Disks available on the market, a single solid state disk can do about 50k IO/s read or 12k IO/s write. So in fact it is about 100x faster than a 15k RPM harddisk."

A fast array controller capable of delivering 500k I/Os would hard pressed to keep up with just 10 SSDs.