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!

Decoding the academic paper

First I started with what appears to be the only paper on the subject; “Energy Intensity of Computer Manufacturing: Hybrid Assessment Combining Process and Economic Input-Output Methods” by Eric Williams of the United Nations University in Japan, and published in Environmental Science & Technology in 2004.

Unfortunately the paper bundles CRT (old-style monitor) production in with the figures which really muddies the waters, especially given that they are redundant technology) However, there seems to be one very nice bit of information embedded in the paper – a table listing the electricity, fossil, and total energy use in computer production. A quick bit of analysis: The total estimated cost of production is 6,400MJ, and if we remove the CRT-specific bits, we take off:

• CRT manufacture/assembly: 255MJ
• bulk materials – CRT 800MJ
• printed circuit boards: 20MJ (est)
• electronic chemicals: 200MJ (est)
• other processes: 400MJ (est)
• Total: 1,675MJ

So, from the paper a PC’s production is about 4,700MJ, which is 1,300kWh. At a green IT conference at Oxford University last year, Fujitsu gave a great presentation on their new super-green PC fabrication plant, and asserted that their range of green PCs took 730kWh to make (materials, production & distrubution). If his numbers are right that is an impressive improvement in 4 years, but Fujitsu have been working hard in the area. Of course, that does also depend on my estimates of what proportion are down the the CRT – I shouldn’t think I’m far off though (I’m good with numbers ).

As an aside, this is very interesting from a recycling point of view. Most PC manufacturers, be it Fujitsu, Dell or IBM will proudly telling us about less than 2% goes to landfill, but if you think about it surely the only energy that can be “reclaimed” from manufacture would be the bulk materials; all the energy of making chips, assembly, PCBs, transport etc is entirely lost. Therefore, in reality one could at most hope to recover perhaps 800-1,000MJ of the original energy-cost (ie. about 20%).

A server is just a PC with a slightly different set of components (an extra disk & more RAM, but less additional cards like graphics & audio), so I think it is reasonable to assume they are similar. Therefore, I pick a figure half way between what I have deduced from the paper (1,300 kWh) and the only convincing figure I have had from a vendor (730 kWh) and have gone for 1,000 kWh in my estimations.

Sweat the desktops

So what about the fabrication energy vs. utilisation? Well, I think the paper’s 81% fab, 19% use lifetime cost is probably no longer very accurate. First, he assumes 3 hours per day, which is far too low given the number of office PCs out there and the often intensive use of family PCs. Second, I think a 3 year lifetime is too low – most people I know use their PCs much longer (they get passed down / re-used rather than thrown away) – I believe the Fujitsu figure of 6.6 years for home users at least.

I would not, however, disagree totally with his figure of 128W for PC+screen – the gains we have made in LCD screen efficiency have been outweighed by power-hungry CPU-intensive machines in recent years, although that trend is reversing. Fujitsu’s figure was 80W for their “green” PC in full power mode, and an average LCD screen uses about 20W (about half a similar CRT).

So, a quick updated estimate (based on an average of PC & home use):

120W * 5 hours/day * 365 * 5 years ~= 1,100 kWh

If we assume LCD screens are as energy intensive as CRTs and go with Eric’s figure of 1,700 kWh for production then the ratio is 61% fab : 39% use.

If we assume that Fujitsu are telling the truth though then it is 730kWh in fabrication, plus ~300kWh for a screen (a guestimate – it is about 465 kWh for a CRT), giving about 1,000kWh fabrication then the embedded vs. use energies are almost equal.

If one then does the calculation based on an office PC usage pattern and a 6.6 year lifetime, then even with more energy efficient PCs the ratio is more like 35% fab : 65% use.

Therefore, I think that we can conclude that the ratio of production energy to usage energy for a PC (with or without screen – the proportions seem about the same) range widely from something like (35% fab : 65% use) to (70% fab : 30% use), and that the main determining factor is the usage pattern of the PC, which is also the one bit of data that we probably have the worst grasp on. Either way, though, you will use less energy overall if you sweat the desktop PCs, as we discussed in the recent BCS Green IT debate.

Replace the servers

The situation is very different for a server, however. A typical modern 1U pizza-box server will use 80W when idle and 140W when working hard. Most of the time they are not straining, so call it 100W:

100W * 24 hours/day * 365 * 1.25 PUE ~= 1,100 kWh per year

In other words, a server uses about the same amount of energy as was required to create it every single year, and the same amount that a PC with a fairly average usage pattern uses in 5 years.

Because of this it is worth while to replace servers with more efficient models on a fairly regular basis. Moore’s Law (that transistor density doubles every 18 months) means that server work capacity per Watt is increasing by a factor of 4 every 3 years. This means, that provided you are using the servers properly (virtualisation etc) and consolidating onto a smaller number of newer machines, if you replace a 3 year old server its 1,000 kWh embedded energy cost will be saved by the 3 you are turning off (4:1 consolidation) in only 4 months.