Server virtualisation is fast becoming a universal technology, with much talk about its reliability and scalability. This overlooks the fact that it is also incredibly useful for smaller organisations, such as housing associations, and does not need much training to use it. Server virtualisation is suitable for almost every organisation that we’ve come across.
There are three main server virtualisation products on the market: VMware ESX; Citrix XenServer; and Microsoft Hyper-v. All three are excellent products, with their own advantages and disadvantages, and all three use virtual machines (VMs) with the operating system installed inside the VM. For now, let’s look at the general benefits of server virtualisation.
There are many benefits of virtualisation. For smaller housing providers, power, space and cost are important considerations. Powering one server is much cheaper than powering four to ten servers. Housing one server is cheaper than constructing a dedicated space for a rack of machines, and means that far less money is spent on networking equipment. Software and maintenance costs also drop noticeably. Finally, buying one server is clearly cheaper than buying many.
For me, having remote access to every aspect of the hardware is paramount. I know that iLO and other IP-based products also allow this, but not the way that VMs do. If a server is low on memory, I can boost its RAM, even while working from home. I can increase CPU cycles or even the number of processors. I can even allocate more hard drives, change the CD or attach a floppy, or add a new NIC.
Another benefit that smaller organisations can enjoy is rapid server provisioning: a server can literally be built within five minutes. There are no conversations about being able to afford it, or making sure it is required. In the same way, virtualisation allows you to have development servers fully isolated from production servers. You can even keep backup copies of VMs when doing upgrades, to revert back to in seconds. Finally, you can keep backup copies of critical VMs to power up within seconds of a failure of the primary VM. You now have redundancy and DR for pennies.
I have deliberately not mentioned any of the enterprise features of virtualisation as I want to demonstrate that virtualisation is worthwhile even without them. However, if you want to spend a little extra, it gets even better still.
First, there are high-availability features; if your physical host server fails, VMs can restart on another host server in a few minutes without the need for manual intervention. With features such as XenServer’s Livemotion, running VMs can be moved across to other physical hosts for maintenance or if you want to use the resources of another host.
Second, there are also resource pool features which can migrate the VMs automatically whenever one host is too busy. You can group servers into resource pools to have greater control over which resources they can take and when, with idle memory and CPUs re-allocated to other VMs.
Although distributed features require SANs, virtual SANs are now available. Although these are merely local hard drives that look like SANs to the virtualisation software, this is the best option for most housing providers. There is no need for fibre-channel HBAs or expensive storage arrays – just load two physical servers with large hard drives and enjoy the full benefits of server virtualisation on a shoestring budget.
In summary, server virtualisation has advantages for all sizes of housing provider. The main benefits of server virtualisation are massive cost savings, excellent monitoring, rapid provisioning and remote hardware manipulation, while additional licensing delivers better availability. Every housing provider should consider virtualisation before investing in any new hardware.
Bobby Maheru is director and senior virtualisation engineer at Xen House.
