Requirements and Limitations

This section will explain the preliminary requirements and limitations to quickly get you familiar with Virtual Machine Manager, as well as help you configure your Synology NAS before you start creating a cluster.

Host

A host is a Synology NAS that contributes computing or/and storage resources in a cluster. In Virtual Machine Manager, you can have up to seven hosts in a cluster.

Virtual Machine

In Virtual Machine Manager, you can create multiple virtual machines. A virtual machine can run on one host, and you will be prompted to choose its host the first time you power on the virtual machine. Its operating system, also known as the guest OS, can be chosen from the system images, and it will be automatically installed upon creation. You can also migrate computing resources of a virtual machine from one host to another. Live migration refers to the process of moving a running virtual machine between hosts without disrupting its availability and connection.

High Availability

You can enable the High Availability feature on the virtual machine if there are at least three hosts in the cluster. To enable High Availability, you must choose one host as the active server and another as the passive server. If the active server malfunctions while the passive server is functioning normally, the system will automatically perform a switchover without disrupting the availability and connection of the virtual machine. On the other hand, if the active server is inaccessible or the virtual machine is unexpectedly offline, the system will perform a failover.

Cluster

A cluster in Virtual Machine Manager contains the following resources:

• Computing resources: The CPU and memory on your Synology NAS will be allocated to be used by the virtual machines on the host. Memory will be reserved by the host.
• Storage resources: The volume created on your Synology NAS will be used as the storage to store virtual disks and data of the virtual machines on the host. The storage will be thin provisioned.
• Network resources: The physical network adapters on your Synology NAS can be used as uplinks for virtual switches, and you can connect the network interfaces on the virtual machines to one or more virtual switches.

Package Integration

• Synology High Availability
  

  Virtual Machine Manager works with Synology High Availability for better availability. However, you must set up an SHA cluster before installing and using Virtual Machine Manager. For further information, please refer to Synology High Availability.

  Note:

  • If you wish to set up Link Aggregation, please enable Open vSwitch and create a new Bond before creating an SHA cluster and using Virtual Machine Manager because Bonds cannot be added or edited in an SHA cluster.
  • New host cannot be added to the VMM cluster after the SHA cluster is created.
  • Virtual Machine Manager will reserve at least one CPU thread for the host in an SHA cluster. To reserve more CPU threads, refer to this article for detailed steps.
• Active Backup for Business
  

  Virtual Machine Manager works with Active Backup for Business, serving as a temporary disaster recovery site for virtual machines. Please note that there are some limitations to the instant restored virtual machines:

  • The following actions are not supported:
    • Clone
    • Migration
    • Snapshots
    • Running on a remote host
    • Adding extra empty disks
  • The High Availability feature is not supported.
  • You cannot create protection plans for the virtual machines.