[mmt]

> If it can fit in RAM, it ain't Big Data. Multiple TBs fit in RAM

To be fair, the price for that RAM starts to steepen at (if not before) the 4TB mark, and 1.5TB might have been the limit on frugal main memory as recently as a year and a half ago.

OTOH, SSDs are very fast even at low cost, so I'd argue if it can fit in directly-attached storage whose aggregate bandwidth compares with the RAM's bandwidth, it ain't Big Data, either. Though even a single PB might be big enough, if the CPUs are too slow.