Software for aggregating a shared pool of virtualized computing and storage resources into a multisite grid which supports the hosting of virtualized desktops; software for enabling a service provider to build a secure, multi-tenant cloud computing environment for hosting virtualized desktops on behalf of distinct customer organizations; software for isolating virtualized desktops of one organization from another on a shared hosting infrastructure; software for connecting end-users to server-hosted virtualized desktops over private and public data networks