re: Is Server-Based Storage Tiering Right For You?
On this topic, a real competitor to server-side flash caching is not actually network storage (which serves a different purpose altogether), but rather plain old DRAM. The server-side caching provided by Lightning (VFCache) is read-only. As a result, persistence is not critical. Compared to a 300GB PCIe SLC flash card (formatted capacity closer to 260 GB) at $15/GB (about $4500), you can add 256GB of DRAM for about $3000. DRAM is not only less expensive, it is vastly faster, does not tie up a PCIe slot, does not require special blade form factors, does not require host-based software, and is something the server manufacturer can easily integrate without cracking open the box. If small in size and read-only, server-side flash cache is of rather limited utility in comparison, at least in the current first generation that suffers from limited VMware support, SLC's high cost, and a lack of write caching.
Any form of server-side caching, whether DRAM or PCIe flash, is of course complimentary to high-performance network storage. In fact, the performance gains of server-side caching are incremental to the performance gains provided by flash-based network storage. In short, adding more memory-based technology instead of spindles...server-side and network storage-side...is always a good thing.