This topic explains how to calculate the capacity of a VSA cluster with 4, 6, or 8 hard disks per ESXi host and a RAID10 configuration.

The capacity of the VSA cluster that uses this configuration depends on two variables.

Total hard disk capacity per ESXi host

Number of ESXi hosts in the VSA cluster (2 or 3)

The capacity of a VSA datastore equals the total hard disk capacity of the ESXi host divided by 4. This is due to the RAID10 configuration on each ESXi host and the mirroring of VSA volumes between VSA cluster members.

Determine the VSA datastore capacity by using the following formula.

VSA datastore capacity = hard disk capacity of an ESXi host / 4

Where

hard disk capacity of an ESXi host = the total capacity of the hard disks that are installed internally on the ESXi host

If you create a VSA cluster with hosts that have different total hard disk capacities, the lowest hard disk capacity from all ESXi hosts becomes the basis for calculating the capacity of every VSA datastore. In such a situation, some of the total hard disk capacity remains unused.

Hard disk capacity per ESXi host = 8TB
Total hard disk capacity of all ESXi hosts = 24TB
VSA datastore capacity = 8TB / 4 = 2TB
Total VSA cluster capacity = 2TB * 3 hosts = 6TB
Hard disk capacity of ESXi host 1 = 6TB
Hard disk capacity of ESXi host 2 = 8TB
Hard disk capacity of ESXi host 3 = 8TB
Total hard disk capacity = 22TB
VSA datastore capacity = 6TB / 4 = 1.5TB
Note

The lowest hard disk capacity of all ESXi hosts becomes the basis for determining the capacity of all VSA datastore.

Total VSA cluster capacity = 1.5TB * 3 hosts = 4.5TB

In this example, the VSA cluster capacity is only 4.5TB

Note

Because this scenario underutilizes the hard disk space of the ESXi hosts that have more capacity, you should ensure that all ESXi hosts have the same hard disk capacity.