IOPS: I/O operations per second. If you pay Amazon for Provisioned IOPS, they will guarantee that you can fetch at least N contiguous blocks of bytes per second, for at least 99% of seconds.

Striped 1000-IOPS EBS volumes: Two volumes, each with 1000 provisioned IOPS, arranged in RAID-0 to get roughly twice the bandwidth of a single volume.

Memory warmup time: From the time you start a long-running task (a database process in this case, from the sound of it) until your memory contents have reached a steady state. At this point, everything you need frequently is loaded into memory, so your I/O traffic will be representative of steady state, rather than an artifact of loading in a bunch of stuff at the beginning of the task/process.