Today Western Digital did a slight rearranging of their enterprise product lineup:

Starting from the top down, the Xe series is essentially a SAS version of their 2.5" 10k RPM VelociRaptor form factor, available in 300GB, 600GB, and 900GB capacities. The Re series is the same 'RE' we are all familiar with, and is now available in both SAS and SATA. That bottom block, however, is something new:

The Se series is Western Digital's attempt at a lower cost Re series drive, and will be available in capacities up to 4TB. 

So the Se is an Advanced Format version of the Re, designed for reduced workloads. Throughput is slightly reduced due to differences in track geometry, though WD let me know they expect final shipping Se's may be closer to the Re spec than the slide indicates. The Se carries the same RPM as well as StableTrac (where the spindle is supported at both ends), RAFF (where accelerometers compensate for chassis vibration), and TLER (where IO request timeouts are adjusted to play nicely with hardware RAID).

The key to the success of the Se will be just what sort of reduced cost Western Digital is able to price the drive at. That information, as well as a full review of an Se, will be coming later today, just as soon as our next batch of samples arrives.