The diagram shows what we agreed we mean by Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and Software as a Service (right hand side) and the areas encompassed by the individual terms infrastructure / platform / software on the left. A better term than “software” might be “application” since the platform part is also really just software, but SaaS has already gained wide acceptance.

It is assumed that “as a service” means all services within the definition are fully integrated up to and including the respective level, thus incorporating any sub-levels. Therefore, SaaS providers could either sub-contract to a PaaS provider, or would incorporate the PaaS themselves and provide it as part of the SaaS “stack”. In turn the IaaS could be sub-contracted or incorporated. The customer would see an integrated service.

It is also worth explaining the overlap between ‘platform’ and ‘software’; that is because some advanced platforms are built on complex software solutions which go well beyond just operating systems and a bit of infrastructure software.

For example, one could consider bare operating system as the platform, with the bespoke software application incorporating its own software infrastructure elements (eg. a bespoke CRM solution). One might also consider a Linux-Apache-MySQL-PHP stack as the platform in its entirety, with only the PHP code itself being the software/application layer. The key differentiator between ‘platform’ and ‘software’ is that a platform is standardised and to an extent commoditised, with the software being the bespoke / custom element. A platform would also often, but not always, be highly scalable across multiple servers.

Standardised / commoditised software (hosted application) services, as opposed to bespoke / custom deployments, would most likely be considered to be SaaS.

Virtual differences

Until this point many experienced readers might be saying, “Yes, that that is just hardware, middleware and software renamed!”. To a large extent you would be right, with one small exception being subtle differences between modern platform/middleware, but there is an important difference between the old concept of “hardware” and ours of “infrastructure”: virtualisation.

It was agreed among the G-Cloud team that the virtualisation should now be considered as part of the hardware layer since it has become such an integral method of dividing and provisioning hardware resources. It is important to note that we drew the line precisely between the virtualisation layer (ie. the hypervisor) and operating system, viewing a bare-bones virtual machine without operating system or kernel as the unit(s) of hardware.

Of course, virtualisation is not ubiquitous. Indeed for many systems including highly scalable ones upon which PaaS and SaaS stacks are built do not use any virtualisation (Google App Engine does not, for example). In such cases one would simply view the stack without the virtualisation layer with the boundary between infrastructure and platform being between the physical hardware and operating system layers.

Network

Another critique of this model could be that the “interconnecting network” appears to link directly from the software layer through to the client device. In reality, of course, all network traffic has to sink back down through the layers from the software to via the networking & firewalling layer, then on to the client device. To keep the stack looking like a stack, however (which is correct from a logical perspective), it is better to stick the client device on top rather than off to one side. In the full postulated functional of the G-Cloud logical architecture the connections are more explicitly shown in a 2D rather than linear model. Hopefully that will be in the public domain soon!

• What does it take to be really green?
• What needs to be in IT policies?
• How can we tell myth from truth in an emotive area?

The protagonists:

• Chair: BCS managing editor Brian Runciman.
• Tracey Rawling Church from Kyocera Mita
• Louise Richards, chief executive, Computer Aid International
• David Critchley, director of retail and professional services at Cisco
• Kate Craig Wood, managing director of Memset and a member of the BCS Data Centre SG

I was at the preview of this tool on 30th April in Southampton Street, and it is an amazingly powerful tool. It allow you to rapidly put together a simulated version of your data centre (including characteristics of everything from power cables to server virtualisation systems to external temperature variation), and then ‘run’ it over a period of time to see the costs and power requirements.

During the demonstration in April, Liam & Zahl (the technical and business brains behind the project) used the tool to great effect, neatly and intuitively demonstrating some of the following:

• The inadequacies of DCiE/PUE as useful a metric due to variation with light work loads; you need to measure facilities power and IT power separately.
• How virtualisation drops the total cost of a datacenter by 75% or more (or you can migrate to us and save >85% of course .
• How simply changing from nameplate (typically >400W on the label on the back of a£1,000 1U server) to peak power provisioning (most modern 1U servers never use more than 150W) reduces the 4-year lifetime server cost from £8,000 to just £5,000.
• That a modular build-out is good, but to be most energy- & cost-efficient you really need a dynamic modular approach so that you can switch M&E equipment on/off with diurnal load variations.
• How data centre costs vary with geo-location! Putting it in Iceland does not save you much after all, contrary to popular belief.

The simulator itself is a pure command-line driven tool that has been released under an open source software licence (OSL V3.0), but there is a Web-based interface that is now available to DCSG members, here, although you will need to read the user guide first unless you have a brain the size of a planet.. If you are a member of the BCS but not of the DCSG, you can find out information here: bcs.dcsg.org. If you are not a member of the BCS but are British and an IT professional, then shame on you!

The beta test is likely to last until Autumn, and feedback is welcomed so that the tool can be further improved and any bugs ironed out. Also, the Carbon Trust and BCS are looking for members willing to trial the tool on a case-study basis over the next few months. If you are interested, visit the Carbon Trust data centre sub-site.

Materials, manufacture and distribution of an average PC currently in use today is is between 750 kilo Watt hours (kWh) for the most modern “green” PCs, and 1,300 kWh for machines of a few years go. You then have to add on about 300kWh for a LED screen (500kWh for a CRT screen). Even if we take the best case scenario we are still looking at a minimum of 1,000kWh for a desktop system, and laptops will only be a little less (most of the energy in PC manufacture goes into making the small, complex components such as chips).

An average PC made within the last few years, with its screen, uses about 100W when powered up and 3W when in hibernate mode. If we assume that the PC is on for 8 hours per day, 5 days per week, and is hibernating overnight we get 200kWh/year “on” usage and 20kWh/year standby usage.

So, a 3-4 year old PC probably used 1,200kWh to make and uses 220kWh/year to run, whereas a modern super-green PC might use 1,000kWh to make and burn 150kWh/year. To look at it financially, you will save about £7/year by switching to a super-green PC. Therefore it makes neither financial nor environmental sense to swap out old PCs before about 6 years. If you need to update the software, then switch to some sort of virtual desktop infrastructure instead and use the PCs as thin clients.

The same sums applied to servers on 24/7 are quite different though. An average £1,000 1U rack-mount server bought 3-4 years ago probably “cost” about 1,000-1,500kWh to make and uses 120W at moderate load, which over a year is 1,050kWh, or at least 1,500kWh when data centre cooling is taken into account. The latest equivalent “green” servers use as little as 80W, so swapping to energy efficient servers will save 400kWh/year in electricity and get you 2-4 times more performance.

With good use of virtualisation to consolidate existing applications onto a smaller number of machines (thus taking advantage of the performance improvements) it makes clear environmental and economic sense to replace machines after 2-3 years. Alternatively, if IT is not your core business activity then you could always consider outsourcing your server infrastructure to a carbon neutral IT host such as Memset of course.

As for the old servers, why not give them away to Africa via Computer Aid International, where our “outdated” hardware is much needed and will be put to good & efficient use (ie. it will only be on when they need it).

Addendum June 2009: There are some very cool technologies like Very PC’s Greenhive (a hybrid between PCs and thin client) which are changing the argument around replacing desktop PCs.

Thin client is also reaching maturity now that you can get a decent amount of bandwidth from ADSL and that Windows Server 2008 includes most of the functionality of Citrix at no extra charge. Thin client is definitely the future I think.