When you enable Virtual SAN on a cluster, choose a disk-claiming mode to organize devices into groups.

Virtual SAN 6.6 and later releases have a uniform workflow for claiming disks across all scenarios. It groups all available disks by model and size, or by host. You must select which devices to use for cache and which to use for capacity.

Create a Disk Group on a Host

When you create disk groups, you must manually specify each host and each device to be used for the Virtual SAN datastore. You organize cache and capacity devices into disk groups.

To create a disk group, you define the disk group and individually select devices to include in the disk group. Each disk group contains one flash cache device and one or more capacity devices.

When you create a disk group, consider the ratio of flash cache to consumed capacity. Although the ratio depends on the requirements and workload of the cluster, consider using at least 10 percent of flash cache to consumed capacity ratio (not including replicas such as mirrors).

The Virtual SAN cluster initially contains a single Virtual SAN datastore with zero bytes consumed.

As you create disk groups on each host and add cache and capacity devices, the size of the datastore grows according to the amount of physical capacity added by those devices. Virtual SAN creates a single distributed Virtual SAN datastore using the local empty capacity available from the hosts added to the cluster.

If the cluster requires multiple flash cache devices, you must create multiple disk groups manually, because a maximum of one flash cache device is allowed per disk group.


If a new ESXi host is added to the Virtual SAN cluster, the local storage from that host is not added to the Virtual SAN datastore automatically. You have to manually create a disk group and add the devices to the disk group in order to use the new storage from the new ESXi host.

Claim Disks for the Virtual SAN Cluster

You can select multiple devices from your hosts, and Virtual SAN creates default disk groups for you.

When you add more capacity to the hosts or add new hosts with capacity to the Virtual SAN cluster, you can select the new devices to increase the capacity of the Virtual SAN datastore. In an all-flash cluster, you can mark flash devices for use as capacity.

After Virtual SAN has claimed devices, it creates the Virtual SAN shared datastore. The total size of the datastore reflects the capacity of all capacity devices in disk groups across all hosts in the cluster. Some capacity overhead is used for metadata.