With Virtual Machine Manager, you can run virtual machines on selected models of Synology NAS. This FAQ will guide you on how to calculate the number of virtual machines that you can run on your Synology NAS, with recommended numbers at the end of the article.

Understanding Memory Requirements

The number of virtual machines that you can run on your Synology NAS is determined by the following:

• Memory available for all virtual machines: This can be calculated after you know the system reserved memory.
• Memory required by each virtual machine: This is determined by the specifications of virtual machines.

• System reserved memory
  • After you know the size of system reserved memory, you can calculate how much memory will be available for VMs.
  • If your Synology NAS has 8 GB memory, DSM will reserve 1.5 GB for system use and provide 6.5 GB for VMs. If your Synology NAS has 16 GB memory or above, DSM will reserve 10% of the total memory for system use and provide the rest of the memory for VMs.
• Specifications of virtual machines
  • Each physical CPU thread can offer 2 vCPUs. You can refer to this article to know how many CPU threads are supported by your Synology NAS.
  • Resources for the hypervisor: Each VM requires 128 MB; each vCPU requires 80 MB; each vDisk requires 32 MB.

Examples

This section takes DS1517+ (8 GB) as an illustrative example when running virtual machines with different specifications.

• DS1517+
  • Total memory: 8 GB
  • System reserved memory: 1.5 GB
  • Memory available for VMs: 6.5 GB (6656 MB)
  • Number of physical CPU threads: 4
  • Maximum number of vCPUs: 8 (4 x 2)

• Virtual Machine A
  

  2 vCPUs + 2 GB memory + 2 vDISKs
  This VM's memory consumption will be: 128 MB + 80 MB x 2 + 2 GB + 32 MB x 2 = 2400 MB
  DS1517+ (8 GB) can run 2 virtual machines with the same specifications as Virtual Machine A. For the third one, the NAS is short of 544 MB (6656 MB - 2400 MB x 3 = -544 MB).

• Virtual Machine B
  

  1 vCPU + 1 GB memory + 4 vDISKs
  This VM's memory consumption will be: 128 MB + 80 MB + 1 GB + 32 MB x 4 = 1360 MB
  DS1517+ (8 GB) can run 4 virtual machines with the same specifications as Virtual Machine B. For the fifth one, the NAS is short of 144 MB (6656 MB - 1360 MB x 5 = -144 MB).

• Virtual Machine C
  

  4 vCPUs + 4 GB memory + 8 vDISKs
  This VM's memory consumption will be: 128 MB + 80 MB x 4 + 4 GB + 32 MB x 8 = 4800 MB
  DS1517+ (8GB) can run 1 virtual machine with the same specifications as Virtual Machine C. For the second one, the NAS is short of 2944 MB (6656 MB - 4800 MB x 2 = - 2944 MB).
  However, this NAS still has 1856 MB (6656 MB - 4800 MB) left to run 1 Virtual Machine B when 1 Virtual Machine C is already running.

Recommended Number of Virtual Machines

The table below shows the recommended number of virtual machine instances to run on supported Synology NAS models: