VMware View Manager 4.5 Admin Manual page 91

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.
I This feature is designed for specific storage configurations provided by vendors who offer high-
MPORTANT
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:
You can specify only one separate replica datastore for a pool.
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If a replica datastore is shared, it must be accessible from all ESX hosts in the cluster.
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If the linked-clone datastores are shared, the replica datastore must be shared. Replicas can reside on a
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local datastore only if you configure all linked clones on local datastores on the same ESX host.
This feature is supported in vSphere mode only. The linked clones must be deployed on hosts or clusters
running ESX 4 or later.
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.
Linked-Clone Desktop Data Disks
View Composer creates more than one data disk to store the components of a linked-clone desktop.
OS Disk
View Composer creates an OS disk for each linked clone. This disk stores the system data that the clone needs
to remain linked to the base image and to function as a unique desktop.
QuickPrep Configuration-Data Disk
View Composer creates a second disk with the OS disk. The second disk stores QuickPrep configuration data
and other OS-related data that must be preserved during refresh and recompose operations. This disk is small,
typically about 20MB. This disk is created whether you use QuickPrep or Sysprep to customize the desktop.
If you configure separate View Composer persistent disks to store user profiles, three disks are associated with
each linked clone: the OS disk, the second desktop disk, and the View Composer persistent disk.
The second desktop disk is stored on the same datastore as the OS disk. You cannot configure this disk.
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Chapter 5 Creating Desktop Pools
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