As we worked through our discovery process of Nimble Storage and it’s amazing claim that it solves the performance vs. capacity trade-off, we stumbled upon an interesting concept….not using the Flash reservoir for write caching. Using the flash only for true, read caching instead of an additional, higher performing storage tier seemed foreign until we read the blog post by co-founder Umesh Maheshwari.
Flash memory shines on reads: it reads 100 times faster than a disk. But its performance advantage is much weaker on writes, and its write endurance is much lower than disk’s. Therefore, Nimble OS uses flash only for accelerating reads, aka “read caching”. It uses NVRAM (a DRAM-based device) for accelerating writes, aka “write caching”.
As with all technology trade-offs, emerging companies without the legacy customer base using older techology have an advantage. New concepts and methods are available to newer companies like Nimble that can architect efficient use of advanced multi-processors, DRAM and flash. In Nimble’s case, they have built an efficient DRAM to disk layer that eliminates the need for a middle flash tier. Flash can be used for what it does best; read speed.
See Umesh’s blog post here Write Caching in Flash; a dubious distinction.