Requirements and Limitations

Overview#

The High Availability (HA) feature has requirements and limitations. Review them before you offer High Availability protection to users.

Requirements#

To move virtual servers to a healthy compute resource after a failure, HA requires the following:

• Create and configure a failover domain.
• At least one other healthy compute resource exists in the same failover domain.
• Destination compute resources have enough free CPU and memory to host the virtual servers during evacuation.
• All compute resources in the failover domain use the KVM virtualization type.
• All compute resources in the failover domain use Shared LVM (iSCSI) or NFS (Network File System) storage.

To configure HA protection, see Enabling High Availability Globally and Managing Failover Domains.

Known Limitations#

The following limitations apply to the HA feature:

• A failover domain requires at least two compute resources. A domain with one compute resource cannot provide failover, and the system reports it as Not protected.
• All compute resources in the failover domain must run KVM virtual servers and use Shared LVM (iSCSI) or NFS (Network File System) storage.
• SolusVM does not support Virtuozzo compute resources for HA, even when they host KVM virtual servers.
• Each compute resource must have enough CPU and memory to run virtual servers after a failover.
• A failover domain can contain up to 2,000 compute resources.
• Use dedicated shared storage for each failover domain. Use one storage for each domain. Do not use the same storage for multiple failover domains. SolusVM does not block this setup, but it does not support it. Shared storage creates one lock space, which can cause the domains to interfere with each other’s failover decisions.
• You cannot change the location or the storage of a failover domain after you create it. To use a different storage, create a new failover domain and move the virtual servers to it.
• Manage failover domain membership and the IP blocks of compute resources from the failover domain pages. You cannot manage these settings from the compute resource creation or edit forms. You also cannot attach IP blocks to a compute resource that already belongs to a failover domain.
• You cannot enable HA for a plan that is linked to an offer with a storage tag, because HA places virtual server disks on the failover domain storage. Remove the storage tag from the linked offers first.
• SolusVM places additional disks that you add to an HA virtual server after creation on the failover domain storage, and rejects storage tags for those disks.