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

vSAN 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 specify each host and each device to be used for the vSAN 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. The ratio depends on the requirements and workload of the cluster. For a hybrid cluster, consider using at least 10 percent of flash cache to consumed capacity ratio (not including replicas such as mirrors). For guidance on determining the cache ratio for all-flash clusters, refer to Designing vSAN Disk groups – All Flash Cache Ratio Update.

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

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

Each disk group includes a single flash cache device. You can create multiple disk groups manually, and claim a flash cache device for each group.
Note: If a new ESXi host is added to the vSAN cluster, the local storage from that host is not added to the vSAN datastore automatically. You have to create a disk group and add the devices to the disk group to use the new storage from the new ESXi host.
Claim Disks for vSAN Direct
Use vSAN Direct to enable stateful services to access raw, non-vSAN local storage through a direct path.

You can claim host-local devices for vSAN Direct, and use vSAN to manage and monitor those devices. On each local device, vSAN Direct creates and independent VMFS datastore and makes it available to your stateful application.

Each local vSAN Direct datastore appears as a vSAN-D datastore.