Traditionally storage systems and other storage related services have been delivered as customized systems. This was done to maintain performance and to reduce support costs to the manufacturers. Now with virtualization the storage as an application concept is being applied to virtual machines. The traditional method of a stand alone customized storage system will still have merit for a long time. Certain environments are just going to need the high performance and high reliability of these systems. The other option is to leverage the server virtualization environment and use it to provide a virtual appliance.”]
Source: https://www.darkreading.com/database-security/storage-services-as-a-virtual-machine