White Papers

5 Dell PS Series Arrays: Advanced Storage Features in VMware vSphere | TR1066
2 vStorage APIs for Array Integration
Historically, VMware has treated all storage as just storage—whether local disk, DAS, SAN, or NAS. VMware
did not utilize any of the advanced capabilities that exist in the more-intelligent storage products, but this
changed with the release of vSphere 4.1. VMware now recognizes and uses intelligent storage arrays, such
as the Dell PS Series, and can leverage the array capabilities to the benefit of the virtualized environment
through a set of SCSI primitives. These SCSI primitives, called vStorage APIs for Array Integration (VAAI), are
supported on all PS Series arrays running firmware 5.0 or above.
The current SCSI primitives included in the VAAI integration stack include:
 Full copy
 Block zeroing
 Hardware-assisted locking
 Thin provision stun (requires PS Series firmware 5.1 or above)
 Thin provisioning space reclamation (requires PS Series firmware 5.2 or above)
2.1 Full copy
A common day-to-day IT task involves deploying servers to support new business applications.
Virtualization changed this from a labor-intensive task of racking a server and installing the OS to a simple
task that required only a couple of mouse clicks to deploy a virtual machine from a preconfigured
template. While this change has resulted in substantial time savings, there was still a significant amount of
time spent watching the progress bar as the virtual machine deployed.
Traditionally, the process of deploying a virtual machine involved all of its data being read from the array,
across the network to the VMware ESXi™ host, and then written back across the network to the array. This
placed a non-production workload on both the network and the ESXi host, in addition to the production
workload of the running environment. Now, with the full copy primitive, ESXi can offload this task to the
PS Series array where it can be completed much more efficiently, with a significant workload reduction for
the ESXi host and the network.
The benefits of full copy do not end with deploying virtual machines from templates. They also extend to
virtual-machine tasks such as Storage vMotion, and virtual machine cloning. For more information, see the
document, Virtual Machine Protection with Dell EqualLogic Virtual Storage Manager v4.0.
2.2 Block zeroing
Fault-tolerant virtual machines require virtual machine disks (VMDKs) that are eager-zeroed thick. These
differ from standard thick or thin VMDKs in that the blocks are zeroed out at the time that the VMDK is
created. For large disks, this can take a significant amount of time as each zero is written from the server
to the array, and an acknowledgment of each write is sent back from the array to the server.
With the block zeroing primitive, the ESXi host offloads to the PS Series array the task of zeroing out the
blocks, to which the array immediately issues an acknowledgment, and permits the host to continue