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13 Dell PS Series Arrays: Advanced Storage Features in VMware vSphere | TR1066
6 Introduction to Virtual Volumes for vSphere 6.0
VMware vSphere 6.0 introduces Virtual Volumes, a significant change in how storage is utilized in a
virtualized environment. Enabled by the second-generation VASA Provider included with Virtual Storage
Manager 4.5, this feature enables storage to be virtual-machine aware and for virtual machines to be first-
class citizens in the storage array.
With Virtual Volumes, the day-to-day activities of a vSphere administrator change very little. A virtual
machine is still a virtual machine, and the work flows within vCenter do not change. However, there are
significant changes on the storage side. As described in the following sections, a virtual machine now
consists of a group of volumes on the array. This moves a number of storage-centric tasks into the
domain of the array.
6.1 Benefits of Virtual Volumes
Without Virtual Volumes, cloning a virtual machine or deploying a virtual machine from a template
involves a large file copy operation, which can be accelerated with the VAAI primitive full copy. With Virtual
Volumes, this becomes a volume clone operation, which is completed within a matter of seconds because
it only involves manipulating some block pointers and reserving space. For the vSphere administrator, this
means that creating a new virtual machine takes only seconds rather than minutes.
VMware recommends using traditional virtual machine snapshots for no more than 72 hours with 2-3
delta files in a chain, and warns that the snapshots may decrease performance. The workflow remains
unchanged, but the old delta file snapshots now become efficient, pointer-based snapshots on the array.
This results in rapid creation of snapshots that enable quick restores and can be kept for an indefinite
period of time. While the array firmware permits a volume to have 512 snapshots, the current vSphere
Virtual Volume implementation is limited to 32 snapshots. Even with this limitation, this enables vSphere
administrators to complement their current backup strategy with more-frequent and rapidly restorable
snapshots.
With Virtual Volumes, a virtual machine is now a group of volumes on the array. This enables the existing
PS Series SAN Headquarters (SAN HQ) array-performance monitoring tool to provide detailed I/O analysis
on a per-virtual-machine and per-virtual-disk level. While similar performance metrics can be seen in
vCenter, these are generated from the host side and cannot show the same level and detail that can be
seen on the array side, including the impact of I/Os, latency, and block side on the underlying physical
disks. When coupled with the PS Series vRealize Operations (formerly vCenter Operations) Manager
Adaptor, SAN HQ makes this detailed information available within vCenter Operation. This allows both the
vSphere administrator and PS Series array administrator to see the same information from their preferred
interfaces.
Storage-Based Policy Management, which was introduced in vSphere 5.0, has been updated to also
provide additional granularity. With VASA 1.0, storage providers were limited to providing a single string of
information about volume capabilities, around which a vSphere administrator created a storage profile.
With VASA 2.0, this enabled vSphere administrators to select from the advertised capabilities of the storage