Product guide

256 EMC Ionix ControlCenter 6.1: Taking Control of Your Datacenter
About Virtual Provisioning
Virtual Provisioning overview
Why Virtual Provisioning
Businesses and organizations continually search for ways to both simplify storage
management processes and improve storage capacity utilization. When provisioning
storage for a new application, storage administrators must consider the application's
future capacity requirements rather than simply its current requirements. In order to
reduce the risk that the application will run out of data storage capacity,
administrators have often allocated more physical storage to an application than is
needed. This allocated but unused storage impacts utilization planning and
introduces higher operational costs. In other cases, organizations do not allocate
enough storage. Even with the most careful planning, they cannot accurately predict
the application's data growth. Therefore, it is often necessary to provision additional
storage in the future, which can potentially require an application outage. This is
where Virtual Provisioning can address these challenges, as data devices can be
added to a storage pool to meet the growing trend of applications without
interruptingg a host or application.
What is Virtual Provisioning
Virtual Provisioning builds on the base "thin provisioning" functionality, which is the
ability to have a large "thin" device (volume) configured and presented to the host
while consuming physical storage from a shared pool only as needed. There are two
types of devices in Virtual Provisioning, thin devices (TDevs) and data devices. A thin
device is the device that is configured to customer requirements. It does not have
storage associated with it at first. A data device is an internal device that contains
physical storage chunks that can be associated with "thin device extents," which are
small units of storage. All data devices are organized into pools and are shown as
System Allocated devices. A thin pool is a collection of data devices and TDevs that
are bound together. Within a thin pool, TDevs that are mapped and masked to hosts
are bound to data devices within the virtual pool. Data devices provide the actual
storage used by the host. The thin pool can have data devices that are either
"enabled" or "disabled." This feature is always useful for quick capacity growth or for a
reserve of actual storage that can be reallocated to another thin pool.