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 the virtualization cluster.
A host is a Synology NAS server that contributes computing or/and storage resources in the virtualization cluster. In Virtual Machine Manager, you can have up to 7 hosts in a cluster.
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.
You can enable High Availability 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.
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。
A virtualization cluster contains the following resources:
Before you start setting up the virtualization cluster, please note the following information and configure your Synology NAS servers accordingly:
A virtualization cluster can contain up to 7 hosts. We recommend you set up clusters with an odd number of hosts because clusters work according to the majority. To constitute a majority, more than half of the hosts must be online. That is, if more than half of your hosts are offline, all the services and operations in the cluster will be stopped. Please note that fault tolerance is not supported on clusters that contain less than two hosts.
You need a dedicated cluster network for the hosts so that they can communicate with each other, as well as for the storage traffic if the virtual machine's computing and storage resources reside on two different hosts.
You need to reserve an IP address range for your Synology NAS servers, and set up a static IP address for the network interfaces on each host. Please note if multiple hosts join the cluster, you cannot change the settings of the static IP address afterwards.
Before installing the Virtual Machine Manager package, please set up at least one Btrfs volume on each Synology NAS server. The volume will be used as the storage on which the virtual machines will be stored.
You can enable permissions for local or domain users/groups to manage virtual machines on Virtual Machine Manager. Since local accounts can only be used to log into a single host, we highly recommend you set up domain accounts and join all hosts to the domain server (at Control Panel > Doman/LDAP) for your convenience.