VMware allows for the on-the fly (non-disruptive) adding/removal of individual disks in existing disk groups.

There is a maximum of 5 disk groups (flash cache device + capacity devices) on an individual ESXi host participating in a vSAN cluster. In a hybrid configuration each diskgroup consists of 1 Flash Device + a maximum of 7 capacity devices. This totals to 40 devices per ESXi host, although an average rack server has room for up to only 24 devices.