Q: Does SQL Server 2008 support Hyper-V dynamic memory?

A: The Enterprise SKU of SQL Server supports the hot addition of memory into the OS, and this is how SQL Server treats dynamic memory. So for SQL Server to use hot-added memory, you must be running the Enterprise SKU of SQL Server. With SQL Server Enterprise edition, the physical memory is checked every second, and if the memory has increased, the target memory size for SQL Server is recalculated. This is how the additions from dynamic memory will be seen.

When using dynamic memory, you should ensure that you set a value for SQL Server's maximum memory. Then, in the configuration of the virtual machine (VM), ensure the start RAM is set to 1GB plus the SQL Server's minimum memory value. Set the maximum RAM of the VM to a value larger than SQL Server's maximum server memory.

Note that if you enable dynamic memory for a VM that contains a non-Enterprise version of SQL Server, SQL Server will only see the startup RAM amount configured for the VM, so ensure the startup RAM amount is set appropriately. Other workloads on the server may use additional memory as allocated in the maximum RAM configuration of the VM.