Rackmount NAS units introduced in recent days have been mostly based on the powerful Intel processors, but there is a market demand amongst small workgroups and SMBs for low power NAS devices in that form factor. In order to serve this market, QNAP is launching the TS-421U and TS-420U, both of which are based on the tried and tested Marvell 6282 CPU. The 420U runs the CPU at 1.6 GHz, while the 421U cranks it up to 2.0 GHz. Both units have four hot-swappable bays in a 1U rackmount form factor. There are two GbE ports, two USB 3.0 ports, two eSATA ports and a single USB 2.0 port in front. The PSU is built-in. Internally, the units sport 1 GB of DDR3 DRAM (double...