TCO and ROI
You must also consider the issue of total cost of ownership (TCO) and the return on investment (ROI) of deploying a virtual desktop infrastructure. The savings realized by deploying VDI come from reducing end-user hardware costs, including the cost of the physical device, as well as the costs associated with ongoing maintenance, and the technical and administrative support required to manage multiple instances of desktop operating systems.
As desktop storage is centralized into the infrastructure supporting the virtual desktops, the cost of deployment of the storage piece can be high, as required performance and capacity levels can be challenging to achieve.
You should consider any opportunity to reduce storage consumption as essential within a VDI deployment. There are two space-reduction technologies that fit well with VDI: thin provisioning and data deduplication. Thin provisioning ensures that virtual desktops use only the capacity required to accommodate the data that?s actually written to disk by the host operating system regardless of how much capacity the desktop is actually allocated. So if a desktop?s drive is configured for 20 GB but only 10 GB is actually being used, then the thin volume appears as 10 GB rather than the 20 GB that?s been allocated. Thin provisioning therefore provides the opportunity to size VDI drives based on future requirements without wasting current resources.
Deduplication technology finds common files or blocks within a storage array and eliminates duplicate copies, while retaining metadata and setting pointers to track shared usage. Within VDI environments, deduplication is an excellent technology for storage space reduction. Typically, desktops are built from a master image, which is a customized desktop build created especially for VDI environments. Individual desktops are replicated from the master image by creating clones. The clones yield excellent deduplication ratios, as most of the desktop content is static operating system data. On certain VDI platforms such as VMware View, deduplication is managed within software through the use of replicas and linked clones, which automatically handle the tracking of changed data.
SAN vs. NAS
In any discussion of storage space reduction for virtual desktops, it?s worth spending a moment to address the storage protocol alternatives for VDI deployments. Storage for VDI can use either block (storage-area network [SAN]) or file-level protocols (network-attached storage [NAS]). Both platforms may offer the space-saving features described here, but the implementations differ slightly. The VDI layer typically handles cloning and replication on block-based solutions, but in file-based implementations cloning is performed by the storage array itself. At the outset this may not seem an important distinction; however, it does enable the work of creating clones to be offloaded to the array itself.
Persistent and non-persistent desktops
VDI desktops can be deployed with the ability to retain user configuration settings (such as shortcuts) across boots; these are known as persistent desktops. Non-persistent desktops don?t retain any configuration information between boots and effectively reset the user each time the virtual desktop starts up. In addition, local user data can be provided through mapping to a local file server.
This was first published in June 2012