Those who buy a HP Microserver Gen8 usually go for the entry-level model with Celeron G1610T processor. Since the CPU is socketed, it can be easily replaced.
The Celeron G1610T is a dual core CPU with 2.3 GHz clock and a TDP of 35 watts - therefore it can be passively cooled without any problems. It is important to find a suitable CPU for replacement.
After some research, among other things in the very good collective thread of the Hardwareluxx forum my choice fell on a Core i5 3470T: 2 cores, 2.9 GHz base clock and hyperthreading support (4 threads). The TDP is also at 35 watts, so that the same cooling system can be used.
The result: at least with the current FreeNAS 10 Release Candidate a much faster interface - all input is simply converted more directly. For pure NAS functions the Microserver Gen8 now of course a less overpowered, but FreeNAS also offers the ability to run docker containers and VMs. There more performance never hurts.
With FreeNAS 10, the things for which I currently use a Raspberry Pi: an OpenVPN server, DNS caching, Bittorrent sync, backup etc. will also be available. For this the performance is then certainly useful.