HP 3PAR Solutions Software for vSphere - Manual (Page 5)

2 Overview and Features
This chapter provides an overview of the VMware VAAI extensions and describes the benefits
provided by HP 3PAR VMware VAAI Plug-in 2.2.0 Software for vSphere 5.0.
About VMware vStorage APIs for Array Integration (VAAI)
VMware has identified several primitives that will enable an ESXi host to convey virtual machine
operations to storage hardware at a meta level instead of at the traditional data level. This reduces
operational latency and traffic on the Fibre Channel fabric/iSCSI network. Some of these primitives
enable the storage hardware to participate in block allocation and de-allocation functions for
virtual machines. These primitives, also known as hardware offloads, are typically implemented
in-band from ESXi to a disk array. ESXi extensions to make use of these primitives are collectively
referred to as vStorage APIs for Array Integration (VAAI).
About HP 3PAR VAAI Plug-in 2.2.0 Software for VMware vSphere 5.0
To keep up with new advances in cloud computing, enhanced capabilities are required by the
SCSI layer stack so that SCSI can meet the demands of emerging virtualized infrastructures. There
are currently a number of shortcomings that need to be solved:
•
VMs competing for the same resources. In cloud computing environments, competition for
system resources can limit scalability and performance. While this resource contention is rarely
an issue in smaller environments or vSphere servers that can host tens if not hundreds of VMs
may run up against these system scalability limits.
In these situations, the SCSI reservation bit locks a LUN when, for example, VMDK clones are
made. This precludes large environments from putting large numbers of VMDKs on a single
large LUN since other VMDKs on that LUN are negatively impacted waiting for a SCSI
reservation to complete while a clone is made of that VMDK file.
•
Expediting the creation of VMware initiated VMDK clones. VMware also has the ability to
create its own clones. However, this adds extra overhead to the vSphere underlying physical
server's CPU, memory, and network resources since the clone has to traverse the storage
array, the host, and then go back out to the storage array again.
•
Host overhead associated with zeroing out previously allocated space. vSphere includes the
ability to zero out blocks of data when storage is allocated to a VM. By first zeroing out these
blocks of data, it prevents the new VM from accidently accessing any of the data that may
have been stored on that disk by a deleted VM that previously had access to it. However the
new problem that results is that the newly created VM has to generate excessive amounts of
write I/O and overhead on the physical host and network in order to zero out newly allocated
blocks.
It is these storage specific issues that the vStorage APIs for Array Integration (VAAI) for vSphere
5.0 and the latest release of the InForm OS resolve. By adding three new SCSI commands to the
standard SCSI command set, VMware and HP provide virtualized data centers a more granular
control for scaling virtualized infrastructures. Following are descriptions for these new commands.
About VMware vStorage APIs for Array Integration (VAAI) 5