By Paul Johnson-Oracle on Jan 21, 2010
Measuring in at around 115 x 101 x 27mm (~ 4.5"x4.0"x1.0"), it is only big enough to hold one laptop sized 2.5" SATA drive.
The drive I installed only has 80GB of space. That would run out real quick with my needs, so I decided to get a MediaSonic USB disk enclosure to link up with my server. It can hold up to 4 SATA drives.
The PC sits on top of the enclosure on my bookshelf taking up 8.5" x 5.0" x 6.5" amount of space. This is not only power efficient, but space efficient since I am using 4 x 1TB drives. 4TB total (theoretical), ~2.6TB in a ZFS raidz. If I were to have purchased the 2TB drives, it would be even better.
Doug's blog on the FIT-PC2 gives a good overview on the features of the device and what works. There is no wifi driver and Xorg doesn't work, so you may want to install OpenSolaris on another machine before installing the internal HDD. My server is headless and uses the built-in gigabit ethernet, so I don't care about those issues.
Links and prices