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You can use either the vSphere Command-Line Interface (esxcli) or the vSphere Web Client to change the
default storage policy profiles. Each virtual machine maintains its policy regardless of its physical location
in the cluster. If the policy becomes noncompliant because of a host, disk, or network failure, or workload
changes, Virtual SAN reconfigures the data of the affected virtual machines and load-balances to meet the
policies of each virtual machine.
Reducing Storage Requirements with View Composer
Because View Composer creates desktop images that share virtual disks with a base image, you can reduce
the required storage capacity by 50 to 90 percent.
View Composer uses a base image, or parent 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, a full clone is first made from the parent 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 clones from one
LUN to another or to move linked clones to a Virtual SAN datastore or from a Virtual SAN datastore to a
LUN.
Replica and Linked Clones on Different Datastores
Alternatively, you can place View 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 Virtual SAN datastores, you cannot manually select different datastores for replicas and linked
clones. Because Virtual SAN automatically places objects on the appropriate type of disk and caches of all
I/O operations, there is no need to use replica tiering for Virtual SAN datastores.
Disposable Disks for Paging and Temp Files
When you create a linked-clone pool, 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, View 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 View Composer persistent
disks on a separate datastore. You can then back up the whole LUN that holds persistent disks.
Chapter 15 Reducing and Managing Storage Requirements
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