5.2

Storing View Composer Replicas and Linked Clones on Separate Datastores
You can place View Composer replicas and linked clones on separate datastores with different performance
characteristics.
This flexible configuration can speed up intensive operations such as provisioning many linked
clones at once or running antivirus scans.
For example, you can store the replica virtual machines on a solid-state disk-backed datastore. Solid-state disks
have low storage capacity and high read performance, typically supporting 20,000 I/Os per second (IOPS).
View Composer creates only one replica for each View Composer base-image snapshot on each ESXi cluster,
so replicas do not require much storage space. A solid-state disk can improve the speed at which ESXi reads
a replica's OS disk when a task is performed concurrently on many linked clones.
You can store linked clones on traditional, spinning media-backed datastores. These disks provide lower
performance, typically supporting 200 IOPS. They are cheap and provide high storage capacity, which makes
them suited for storing the many linked clones in a large pool. ESXi does not need to perform intensive,
simultaneous read operations on a linked clone.
Configuring replicas and linked clones in this way can reduce the impact of I/O storms that occur when many
linked clones are created at once. For example, if you deploy a floating-assignment pool with a delete-desktop-
on-logoff policy, and your users start work at the same time, View Manager must concurrently provision new
desktops for them.
IMPORTANT This feature is designed for specific storage configurations provided by vendors who offer high-
performance disk solutions. Do not store replicas on a separate datastore if your storage hardware does not
support high-read performance.
You must follow certain requirements when you store the replica and linked clones in a pool on separate
datastores:
n
You can specify only one separate replica datastore for a pool.
n
If a replica datastore is shared, it must be accessible from all ESXi hosts in the cluster.
n
If the linked-clone datastores are shared, the replica datastore must be shared. The replica cannot reside
on a local datastore.
If the linked-clone datastores are local, VMware strongly recommends that you store the replica on the
same volume as the linked clones. Although it is possible to store linked clones on local datastores and
the replica on a shared datastore if all ESXi hosts in the cluster can access the replica, VMware does not
recommend this configuration.
Availability Considerations for Storing Replicas on a Separate Datastore or Shared
Datastores
You
can store View Composer replicas on a separate datastore or on the same datastores as linked-clone virtual
machines. These configurations affect the availability of the pool in different ways.
When you store replicas on the same datastores as linked clones, to enhance availability, View Composer
creates a separate replica on each datastore. If a datastore becomes unavailable, only the linked clones on that
datastore are affected. Linked clones on other datastores continue to run.
When you store replicas on a separate datastore, all linked clones in the pool are anchored to the replicas on
that datastore. If the datastore becomes unavailable, the entire pool is unavailable.
To enhance the availability of the linked-clone desktops, you can configure a high-availability solution for the
datastore on which you store the replicas.
Chapter 5 Creating Desktop Pools
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