Because Composer creates desktop images that share virtual disks with a base image, you can reduce the required storage capacity by 50 to 90 percent.
Composer uses a base image, or golden image virtual machine, and creates a pool of up to 2,000 linked-clone virtual machines. Each linked clone acts like an independent desktop, with a unique host name and IP address, yet the linked clone requires significantly less storage.
Replica and Linked Clones on the Same Datastore
When you create a linked-clone desktop pool or farm of Microsoft RDS hosts, a full clone is first made from the golden image virtual machine. The full clone, or replica, and the clones linked to it can be placed on the same data store, or LUN (logical unit number). If necessary, you can use the rebalance feature to move the replica and linked-clone desktop pools from one LUN to another or to move linked-clone desktop pools to a vSAN datastore or from a vSAN datastore to a LUN.
Replica and Linked Clones on Different Datastores
Alternatively, you can place Composer replicas and linked clones on separate datastores with different performance characteristics. For example, you can store the replica virtual machines on a solid-state drive (SSD). Solid-state drives have low storage capacity and high read performance, typically supporting tens of thousands of I/Os per second (IOPS). You can store linked clones on traditional, spinning media-backed datastores. These disks provide lower performance, but are less expensive and provide higher storage capacity, which makes them suited for storing the many linked clones in a large pool. Tiered storage configurations can be used to cost-effectively handle intensive I/O scenarios such as simultaneous rebooting of many virtual machines or running scheduled antivirus scans.
For more information, see the best-practices guide called Storage Considerations for VMware View.
If you use vSAN datastores or Virtual Volumes datastores, you cannot manually select different datastores for replicas and linked clones. Because the vSAN and Virtual Volumes features automatically place objects on the appropriate type of disk and cache of all I/O operations, there is no need to use replica tiering for vSAN and Virtual Volumes datastores.
Disposable Disks for Paging and Temp Files
When you create a linked-clone pool or farm, you can also optionally configure a separate, disposable virtual disk to store the guest operating system's paging and temp files that are generated during user sessions. When the virtual machine is powered off, the disposable disk is deleted. Using disposable disks can save storage space by slowing the growth of linked clones and reducing the space used by powered off virtual machines.
Persistent Disks for Dedicated Desktops
When you create dedicated-assignment desktop pools, Composer can also optionally create a separate persistent virtual disk for each virtual desktop. The end user's Windows profile and application data are saved on the persistent disk. When a linked clone is refreshed, recomposed, or rebalanced, the contents of the persistent virtual disk are preserved. VMware recommends that you keep Composer persistent disks on a separate datastore. You can then back up the whole LUN that holds persistent disks.