Updated 3/19/2018 to include new findings based on real-world experience, newer Operating Systems, and best practices.

I am frequently asked to condense Microsoft’s detailed System Specifications for Dynamics GP. Following is a ‘short list’ of server hardware requirements and recommendations that will give maximum performance at reasonable cost:
1. 64-bit hardware platform, Hardware RAID. You want Hardware RAID so the maintenance of the drive partitioning and striping doesn’t fall to the Operating System.  Windows Server 2012 (or later) Standard 64-bit and SQL Server 2012 (or later) 64-bit Standard Edition. 64-bit allows the use of memory over 4GB without disk swap. 1 or more quad-core processors.
2. 12GB RAM minimum.
3. Drive configuration – The recommendation is OS on RAID1 (2 drives), Data on RAID5 (3 or more drives), which is a minimum of 5 drives. One additional often-overlooked factor is drive speed. Use 10,000 RPM drives as a minimum for the data drives, 15,000 RPM preferred. If it’s a matter of size over speed, lower the size (15k RPM is not available in all drive sizes) to maintain speed. For OS, 80GB drive space minimum, for Data, (3 (or more)) 132GB in RAID5, yielding 260+GB of drive space. For maximum performance, add one additional small 15,000 RPM (or Solid State) drive and move the SQL tempdb to that drive. Isolating tempdb will boost SQL performance dramatically.
If you must back off the drive count, go for a RAID5 array of 10,000+ RPM drives in a single partition. In this configuration, partitioning data from OS has no good effect on performance, since all partitions are running on the same drives, and it is the division of tasks by array and spindle that increase performance, not just a cosmetic partitioning.
If the server is virtual, either Hyper-V or VMware architecture is supported. Allocate at least two processors and a minimum of 12GB RAM. Do not permit the host to dynamically allocate RAM. File and folder layout is not critical, however, you must use a fixed disk size rather than dynamic, and virtual disk files MUST be fully expanded at the host on creation. Calculate sufficient space for Microsoft SQL database growth, installation software, and on-disk data backups. Depending on the number of GP companies and anticipated data volume, an 80-120 GB System drive and 200GB data drive should be sufficient.