[QLink]

I can't say definitively, but I'm pretty sure the Microserver supports 3TB drives max. However, if you buy certain mounts you can fit an extra 2 HDDs in the ODD bay up top, allowing potentially 6 hard drives in total

but i can. it definitively does support 3TB HDDs, cause i have already one installed in it running with whs2011, but you cannot boot from a 3TB HDD cause the N36L/N40L only has a "old" bios and no UEFI.
best thing you can do is, use a 2,5" HDD(you can put it in the space between the 5,25" bay and the 4x3,5" HDD-bays) as systemdrive or USB stick.

maybe take a look here. many questions are already answered there and there are also many links to certain microserver projects for example like this which is close to the max what the microserver can handle inside...
another way to increase storage space is using external drive cases connected via SATA to the microserver...