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.