Over the past couple of weeks I’ve had occasion to consider our internal server strategy and how it could be made not only as robust and resilient as possible but also easy for others to administer in my absence (how else will I ever achieve my goal of a three day week? :) ). For the past two years we have operated using a set of virtual servers which has given us the flexibility to manually move any server from one physical box to another relatively easily. VMware server provides the common interface layer (drivers, etc.) to enable this. Recent VMware updates have also made even more possible (depending on how deep your IT pockets are).

For those not familiar with virtualisation, it’s simply a way of allowing a host operating system to run multiple independent guest OSes on a single physical box. The virtualisation software handles process, memory and resource allocations as required within the configured allowances. This allows for better utilisation of resources (in normal circumstances a standard physical server is underutilised) and has the benefit that fewer physical servers are needed, saving on power and air conditioning costs. Correctly configured, even an entry-level server can support at least three virtual machines. In data centres with large capacity rack servers this can easily be twenty or more per physical box. Host operating systems are typically Windows Server or Linux.

The virtual server itself really consists of a small configuration file and a file that acts as the virtual “hard disk”. Simply moving these files to a different physical server with VMware installed allows the virtual server to be run. Moving this on a level, with the cost of network storage dropping it’s quite easy to place these files on a NAS or preferably an iSCSI (SAN) device that can be shared between all the physical servers. It’s then simply a case of the deciding which physical machine to run the virtual files from.

VMware has now released its next generation of products called vSphere which utilise the advances in processor hardware where the processor itself provides direct support for ‘hypervisor’ applications (the application layer that VMware provides). With the lack of a need for a host OS, there’s then a further improvement in performance and resource usage. In its basic form, vSphere provides this hypervisor in the guise of ESXi along with centralised tools to administer the guest servers. vSphere also has versions that cater for most sizes of enterprise, from small organisations up to large multi-national corporations with even the low end solutions providing an amazing level of functionality. For example, vSphere Essentials Plus provides a ‘high availability’ feature, where should one of your physical servers suffer a problem vSphere will automatically detect this and start rebooting the virtual servers affected on a different box for you. Down-time is therefore minimised as is potential data loss. If planned maintenance is required you can simply tell vSphere to ‘move’ affected virtual servers onto another physical machine. Taking this to the next level, the high-end solutions automate this further by constantly mirroring the memory allocation of each running virtual server on at least two physical ones and, in the event of a failure, the mirror takes over instantly without users even noticing any loss of service or data loss.

For many large corporate data centres, the running costs of servers greatly over shadow purchase costs. This is made all the worse out of normal office hours when most servers are sitting idling yet still using considerable power and cooling resources. Using vSphere, the number of physical servers running can be automatically scaled down during periods of low demand by running more virtual servers on fewer physical ones. As demand increases, the dormant servers are “woken up” and resume normal operations. All this happens without any manual intervention and with no loss of service to users.

So all I have to do now is put an expenditure proposal together...

Just to mention, I’ve gone on a lot about vSphere here, and I want to point out that I’m not getting any commission from VMWare! The simple fact is that it seems far and away the better virtualisation software out there at the moment, though Microsoft’s Hyper-V does appear to be catching up...