“For us it’s about redundancy and reducing the number of physical machines.” Peter Shilling, TPP
Most approaches to sharing one physical server between two or more clients involve some kind of software partitioning (such as virtual hosts in Apache or shared hosting in Oracle) or virtual machines (VMs) that run under the control of a host operating system (like Virtual PC under Windows). The downside is that problems occurring within one virtual environment can affect the others, and the hosting services’ clients have very little control over the software environment.
So an organisation requiring a more robust solution would typically use a dedicated server, either by acquiring the hardware, installing it at a co-location facility and taking ongoing responsibility for its management, or by enlisting the services of a managed hosting provider.
Now there’s a third way: virtual machine hosting. This allows multiple operating system environments to run on one physical server with a high degree of isolation. It also allows multiple applications to run on one physical server without sacrificing stability or performance, as well as providing robust support for multi-tenanting.
Sydney-based hosting provider Bulletproof Networks recently launched what it claims is the first such hosted VM service, though Macquarie Hosting has not been far behind in releasing its own such service. Both companies are using VMware.
Other service providers have virtualisation offerings but they don’t always give a dedicated software environment. For example, Virtuozzo (as used by WebCentral) shares one copy of an operating system among multiple partitions.
“VMware Infrastructure 3 really is virtualisation done the right way,” says Lorenzo Modesto, general manager of Bulletproof Networks. In particular, VMware does a better job of preventing one VM from impacting on another than any other virtualisation product, he says.
This is an important issue. Conventional sharing allows providers to oversubscribe their servers on the assumption that different clients’ workloads will not peak at the same time, says Sam Higgins, research director at market research company Longhaus, but VMware guarantees a minimum level of resources to each VM.
“SMEs (small- to medium-sized enterprises) love buying off plans . . . and only paying for what they use,” he says. “Bulletproof is the Virgin Blue of the IT industry.”
Kevin McIsaac, an analyst at IBRS, regards VMware highly: “I can’t see any downside at all,” he says, although he does warn that while organisations can buy exactly the resources they need it can be very hard to determine whether they are getting what they’re paying for. “You shouldn’t care what the raw performance numbers are,” he suggests. Instead, it is more appropriate to measure outputs than inputs using whatever metrics are appropriate for your application, such as delivering a certain number of web pages per second. McIsaac warns that is a difficult task that few organisations do well.
While contracts are based on the provision of VMs with certain CPU (central processing unit) and memory characteristics, McIsaac says organisations should expect honesty from their providers but ensure contracts allow for regular renegotiation.
Write to the Editor at Technology and Business
* All fields are mandatory.