Has this definition changed over the last few years? What trends are shaping this definition?
The definition of high-performance NAS is being shaped more by customer demands rather than industry trends. Customer data sets are actually determining what high-performance is and what is not. These are important business needs such as archiving and e-discovery. Consequently, NAS platforms that can handle those data sets efficiently and quickly today may be deemed "high-performance."
As customer needs and business applications shift over time, the definition of "high-performance" will undoubtedly change for NAS platforms. For example, today's legal discovery or Web 2.0 applications tend to favor short-burst-type NAS access, but have large data sets (there's a lot of data for an e-discovery tool to comb through). IOPS and NFS operations are particularly important to those applications. As more of these applications appear, customers will be demanding higher performance in these areas from NAS platforms, and the vendors will have to follow suit.