Good post by George Crump (thank you)
Caching is a popular first step when data centers want to leverage high performance flash storage. It eases the transition from traditional disk storage by automatically moving frequently accessed data to the high performance pool. Most cache technologies that have come to market have essentially ignored writes and focused instead on read caching. But an increasing number of vendors have started delivering, or announced, write caching solutions as well. While it sounds like a good idea to cache both reads and writes there are some considerations that IT planners need to be aware of when implementing write-based caching.
Read on here