Hybrid is an up and coming enterprise storage architecture, advocated by many legacy storage vendors, that supposedly gives you the best of both worlds: the seasoned storage and reliability architecture of a longstanding enterprise storage leader combined with fast SSD, often from an up and coming SSD startup. One such solution, described in this InfoStor article Gridiron Launches SSD-Accelerated OneAppliance Array, combines NetApp’s E-5400 Series storage array with GridIron’s flash-based TurboCharger Appliance. On its face, this sounds like a great solution, as you get NetApp’s tried and tested high availability, replication, and synchronization features with the fast performance of GridIron’s SSD. However, if you’re considering a solution like this, make sure you ask the right questions.
Is SSD used as a cache or mainstream storage? Many of these solutions, including NetApp’s, use SSD as a cache sitting in front of legacy hard disk storage, not as direct storage. Cache can speed up many applications, but it’s not an ideal solution if you need the absolute highest performance you can get from random, write heavy applications such as online transaction processing (OLTP). First, until the architecture figures out which data to put in the cache you’re going to get slow hard-disk-style I/O performance. Second, with a cache architecture writes are often made directly to hard disk rather than to fast SSD, so write-heavy applications such as OLTP don’t benefit from cache as much as they do from direct SSD storage. Finally, you’re not getting maximum storage efficiency as most of the data in the cache is duplicated on the hard disk.