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 the vSAN Cluster
You can select multiple devices from your hosts, and
vSAN creates default disk groups for you.
When you add more capacity to the hosts or add new hosts with capacity, you can select the new devices to increase the capacity of the vSAN datastore. In an all-flash cluster, you can mark flash devices for use as capacity.
After vSAN has claimed devices, it creates the vSAN 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.