CloudStack volumes and templates are one single virtual disk in case of XenServer/XCP and KVM hypervisors since the files used for templates and volumes are virtual disks (VHD, QCOW2). However, VMware volumes and templates are in OVA format, which are archives that can contain a complete VM including multiple VMDKs and other files such as ISOs. And currently, Cloudstack only supports Template creation based on OVA files containing a single disk. If a user creates a template from a OVA file containing more than 1 disk and launches an instance using this template, only the first disk is attached to the new instance and other disks are ignored.
Similarly with uploaded volumes, attaching an uploaded volume that contains multiple disks to a VM will result in only one VMDK to being attached to the VM.
This behavior needs to be improved in VMWare to support OVA files with multiple disks for both uploaded volumes and templates. i.e. If a user creates a template from a OVA file containing more than 1 disk and launches an instance using this template, the first disk should be attached to the new instance as the ROOT disk and volumes should be created based on other VMDK disks in the OVA file and should be attached to the instance.