Home Is Home: The Physical Practicalities - Smart Home Automation with Linux and Raspberry Pi - page 128

Rack Mount
These can be bought in many variants including those with redundant or dual power supplies and quad processors
being the standard rather than the exception. Consequently, these power houses of processing can handle the
transcoding needs of several users simultaneously, with enough cycles to spare to handle all the other services
(web, e-mail, and so on) without affecting any other user. They are the industry standard for commercial
applications for a reason because they can handle any load, for any length of time, and can run happily for many
years without change.
Unfortunately, they are suitable for home use only if you can place them away from the living areas since they
usually have large noisy fans inside and give off a lot of heat. Although the noise can be muted by placing the machine
in a cupboard, you can't generally achieve the same result by replacing components with low-noise equivalents, as
they're generally not of the standard PC design.
The heat is also something you will need to effectively dispose of. Air conditioning is standard in offices but not
at home where the same effect is generally achieved by opening a window. Running a rack server at home will often
need some kind of extractor fan at the very least.
The non-PC-ness will also hit home when considering its upgrade status. You will not be able to fit a PCI TV card
into many rack machines because the connection form factor and size will be prohibitive. You will also need to buy
a physical rack, or half-rack, in which to mount the unit. These are designed and priced at commercial installations,
and although you will always need some kind of mounting for all the equipment mentioned earlier, there are cheaper
ways of doing it with DIY shelving.
Desktop PC
This is the most popular choice, for all the obvious reasons: they are understandable, common, cheap, and built for
home use. They can also be upgraded easily with additional cards, and replacements for worn-out (or too noisy)
parts are available in your local bricks-and-mortar store. The current range of machines is fast enough to perform
transcoding for a couple of media head units around the house, as well as handle all the other standard tasks.
Unfortunately, the home machine is intended to be used as a home machine, that is, for a few hours in the
evening to check e-mail and play games. Using it as a server, running 24/7, can strain the physical components of
the machine (fans and discs mostly) and increase the risk of breaking the machine's integrity. Unlike racks, these
machines are built to a price point, not a quality factor, and so will use components that allow the price to hit that
magic 299 figure, or whatever. Consequently, these components might have a lower tolerance for temperature
variances (which will happen if the machine is working all day) or have a lower mean time between failures (MTBF).
When the machine is continually accessing data, either from memory or from a hard disk, the chance of this
happening will naturally increase.
My personal setup uses a desktop PC as the media transcoding server, which runs most of the time. I bought
higher in the price range than I would for a traditional desktop machine, with quieter-than-standard fans and better
components. I also bought spares for the fans at the same time so that if I needed to replace the moving parts of the
machine, I would have some available. RAM chips (which are, admittedly, also likely to go bad over time) are usually
available for many years after a machine's release, whereas the particular size of CPU fan isn't. This is because any
server that lasts several years will outlive the current design of processors and motherboards, making spares for these
components very difficult to come by. I also admit that when (not if ) these components finally die, I will probably be
unable to buy replacements and so will have to endure the pain of setting up an entirely new machine.
Mini-ITX
The Mini-ITX is a family of machines based around the 170 ×170mm ITX motherboard. Within this specification,
there are a number of different options with varying processors, graphics chips, and cooling methodologies. This
includes many machines that are fanless, relying only on the heat sink for cooling. This makes them more energy
efficient than their desktop counterparts and suitable for placing in more communal areas, such as the living room
where they are often used as media players.