Adding an SSD cache to a storage array sounds like one of those upgrades that should be immediately obvious. Put flash storage in front of a bunch of mechanical drives, flip the right settings, and the whole thing should feel faster. That was more or less what I expected, and I spent too much time at first looking for a dramatic before-and-after result. What I got instead was narrower, but also more useful once I stopped judging the cache by the wrong workloads: it helped with the small, repetitive storage tasks that made the array feel slow, while leaving plenty of other things almost completely unchanged.