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Hypervisors are the primary component of virtualisation
that enables basic computer system partitioning (i.e., simple
partitioning of CPU, Memory and I/O). VMware ESX Server incorporates
a VMware hypervisor as one of its basic functional elements.
As virtualisation technology evolves and underlying hardware
improves, basic hypervisor functionality could reside in a
stand-alone software layer, in hardware or in software associated
with a particular operating system. An open standard hypervisor
framework will benefit customers by enabling an ecosystem
of interoperable virtualisation vendors and solutions to exploit
standard hypervisor functionality.
VMware will contribute its existing framework of interfaces,
called Virtual Machine Hypervisor Interfaces (VMHI), based
on its commercially successful virtualisation products to
facilitate the development of these standards in an industry
neutral manner. These frameworks and interfaces are described
below.
Hypercall Interface
In a fully virtualised environment, operating systems issue
hardware instructions that are intercepted by the virtualisation
software. In certain situations, however, it may be advantageous
for the operating system inside a virtual machine to directly
communicate to the underlying virtualisation software. The
Hypercall interface defines the mechanism for such communication
to occur. These instructions enable the virtualisation software
to more efficiently use resources of the computer and perform
tasks on behalf of operating systems running in virtual machines,
such as managing memory resources.
Management Interface
These interfaces enable management software (such as those
provided by HP, IBM, VMware, CA, BMC, etc.) to deploy, control
and monitor virtual machines running on different virtualisation
environments. This is beneficial to customers because it allows
management software to automatically execute many of the daily
tasks in the data center. Automation decreases costs and increases
reliability.
As a leader in the computer virtualisation industry, VMware
is actively involved in driving the DMTF virtualisation model
forward. This effort is taking place in the Virtualization,
Partitioning, and Clustering Workgroup - The active participants
include VMware, IBM, HP, Microsoft and others.
Virtual Disk Interface
These interfaces are an important virtual hardware construct
used by all virtualisation platforms. Virtual disks serve
as the container for the disks typically 'seen' and used by
the operating system running in a virtual machine. Virtual
disks can be stored in many ways on a variety of storage systems,
including local or networked storage and as files on host
operating system filesystems. Interoperable formats for virtual
disks across implementations preserve customer configurations
as they move between vendor solutions. Common formats allow
vendors to use the same disk backup, patch management, virtual
machine migration tools for their solutions. This, in turn,
promotes customer choice and increases the number of solutions
available in the marketplace. Lastly, common formats will
allow storage systems to optimise for storage access of virtual
disk data.
VMware intends to provide a royalty-free license to the specifications
for these interfaces as part of the VMHI to collaborating
partners.
Copyright VMware
Inc., reproduced with permission.
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