Windows Server 2008 (not R2) has a problem where you may experience performance issues in applications and services when the system file cache consumes most of the physical RAM

The problem with Windows Server 2008 (not R2) is described here:
https://support.microsoft.com/kb/976618

Memory management in Microsoft Windows operating systems uses a demand-based algorithm. If any process requests and uses a large amount of memory, the size of the working set (the number of memory pages in the physical RAM) of the process increases. If these requests are continuous and unchecked, the working set of the process will grow to consume all the physical RAM. In this situation, the working sets for all the other processes are paged out to the hard disk. This behavior decreases the performance of applications and services because the memory pages are continuously written to the hard disk and read from the hard disk. This behavior also applies to the working set of the system file cache. If there is a continuous and high volume of cached read requests from any process or from any driver, the working set size of the system file cache will grow to meet this demand. The system file cache consumes the physical RAM. Therefore, sufficient amounts of physical RAM are not available for other processes. On 32-bit versions of Microsoft Windows operating systems earlier than Windows Vista, the working sets of the system file cache have a theoretical memory limit of less than 1 gigabyte (GB). The limitation of the virtual address range prevents the working sets of the system file cache from exhausting the physical RAM. On 32-bit versions of Windows Vista operating systems, kernel resources are allocated dynamically. The working set of the system file cache increases to consume the virtual address range of the kernel mode at the expense of other kernel resources. The limitation of this memory range is less than 2 GB. If the computer has more than 2 GB of physical RAM, the cache cannot exhaust all the physical RAM. However, the cache can exhaust the virtual address space in the kernel. This can cause allocation failures for other kernel components. On 64-bit versions of Windows operating systems, the size of the virtual address range is typically larger than the physical RAM. In this situation, the working set for the system file cache can increase to consume most of the physical RAM.

The official and best solution is; if using Windows Server 2008, you need to use 2008 "R2".