Release Notes

8 VMware vSphere Virtual Volumes on Dell PS Series | 2028-N-WP-V
3 Why Virtual Volumes?
Without vVols, cloning a virtual machine or deploying a virtual machine from a template is a large-file copy operation.
While the VMware vSphere Storage APIs – Array Integration (VAAI) Full Copy primitive provides acceleration of these
tasks, these operations are even faster with vVols because they become a SAN volume clone operation. A volume clone
operation (the manipulation of some block pointers and reserving of space on the SAN) is completed within a matter of
seconds. The result for the vSphere administrator is the ability to have a new virtual machine in seconds rather than
minutes.
Without vVols, VMware warns that virtual machine snapshots may decrease performance and recommends limiting
their use to no more than 24 to 72 hours, with 2-3 delta files in a chain. With vVols the workflow remains unchanged,
but the old delta file snapshots now become efficient pointer-based snapshots on the SAN. This results in rapid
creation of snapshots that can be kept for an indefinite period, plus restoring a virtual machine from a snapshot
becomes a rapid operation.
Note: While the Dell PS Series SAN firmware permits a volume to have 512 snapshots, the current vSphere vVol
implementation is limited to 32 snapshots. Even with the limitation, this enables vSphere administrators to
complement a current backup strategy with more frequent and rapidly restorable snapshots.
With vVols, a virtual machine is a collection of volumes on the SAN. This enables the existing EqualLogic SAN
Headquarters (SAN HQ) performance monitoring tool to provide detailed I/O analysis on a per-virtual-machine and per-
virtual-disk level. It is worth noting that the individual VM and VMDK performance metrics provided in vCenter are
generated from the host side, and cannot normally show the impact of I/Os, latency, and block size on the underlying
physical disks. However, SAN HQ is a powerful tool provided with each PS Series SAN (SAN HQ coupled with the
EqualLogic vRealize Operation (formerly vCenter Operation) Manager Adapter) makes this detailed information
available within vCenter Operation. This enables both the vSphere administrator and PS Series storage administrator to
see the same information from their respective preferred interfaces.
Another benefit of vVols is that Storage Policy-Based Management (formerly Profile-Driven Storage) has become more
granular in this implementation. Rather than creating a policy based on all the capabilities of an underlying volume,
vSphere administrators can create storage policies based on the individual capabilities advertised by the pool of the
storage container.
3.1 Virtual Volumes terminology
An understanding of the following vVols-relevant terminology is important while reading this paper.
• VASA Provider:
- The VASA Provider plays an important role in enabling a vVol environment. The VASA Provider offers out-
of-band management access to the SAN from vCenter. It enables vCenter to communicate with the SAN in
ways that the current SCSI protocol does not. Through this communication channel, vCenter sends
operational requests for interacting with the virtual volumes that back virtual volume based virtual
machines.