There's an excellent new article by Duncan Epping available now, which discusses vVOLs, and the use of SSDs for caching VMs. This is a very different approach to using an SSD to read/write cache your LSI RAID controller's array, for example. The cost/viability in a home-lab or test environment is not known, since this stuff isn't even real yet. But still, worth knowing about, as a heads-up about what's coming up, around the corner, down the road. Enjoy!
VMworld session report: INF-STO2223 – Tech Preview vSphere Integration with Existing Storage
by Duncan Epping Sep 7 2012
Here's a teaser/excerpt:
The result of this project should be a framework which allows partners to insert their caching solution and utilize SSD resources more effectively without some of the current limitations.
Virtual Flash may be VM-transparent but also VM-aware. Meaning that it should for instance be possible to allocate resources per virtual machine or virtual disk.
VM-aware caching is a type of caching where the Virtual Flash resource is presented directly to the virtual machine as a device. This allows the virtual machine to control the caching algorithm. The cache will in this case automatically “follow” the virtual machine during migration. It should be pointed out that if the VM is powered off the cache is flushed.