What's a "single point of failure", and why do I need to know?

It's actually a concept that I've become just a little too familiar with in
recent months, in part due to an accident down the road, and in part due to
some aging computer equipment.

If you rely on your network or internet connection to run your business,
then it's important to be aware of what might fail, what the ramifications of
failure are, and what you plan to do when (not if) it fails.

A "single point of failure" is, to oversimplify a little, any single piece
of equipment that, if it fails, can bring your entire operation to a halt.

You may not realize how many single points of failure you have, but it can
be kind of surprising.

One great example is your broadband modem. It's your gateway to the
internet. If you run an internet based business, and your modem fails, your
operation comes to a complete stop.

I had exactly this happen to me some months ago. My DSL modem decided it was
done for, and died a quiet death. My internet connectivity was gone. Given that
the internet is what I'm all about, that had serious impact on my ability to do
business and communicate with friends and clients. On top of that, for various
reasons known only to my phone company, I'm actually stuck with an old style of
DSL technology, which means that replacement DSL modems are difficult and time
consuming to locate. Fortunately I was able to locate one the next day through
a local eBay seller.

I have now also purchased a second DSL modem as a backup. That's part of
understanding the ramifications of that "single point of failure". By
identifying it, you can make contingency plans to recover more quickly from the
failure.

It happened again a couple of weeks ago. Apparently an auto accident down
the road sent a power surge through the phone lines. All of a sudden not only
was my phone dead, but the DSL disconnected once again. My single point of
failure? The circuit board fuses that had blown in my DSL filter. I now have a
replacement in place, and a spare.

By now you can see that almost anything dealing with my DSL line is, for me,
a single point of failure. In larger companies, they'll mitigate this risk by
having multiple different lines coming into the facility. That way any one can
fail, but the operation continues using the other - multiple failures are
required for the operation to be seriously affected.

In truly serious datacenter operations, even the conduit that carries the
wire can be a single point of failure. If all those multiple different lines
come in through the same conduit outside the building, a single backhoe can
take them out all at once. (Never underestimate the power of a backhoe.) The
solution that large datacenters take is to ensure that different lines come in
to different physical locations.

But back to your small business. What are your potential single points of
failure? Consider these, if your business is dependant on them:

• Your internet connection. What happens if your internet connection
  goes away?

• Your networking equipment. A router or switch could die. Do you know what
  you would do?

• Your cash register or other data processing equipment. For example, my
  wife's retail store is dependant on a single computer as its cash register. We
  have a backup plan - do you?

• Your printer. Are you required to print receipts or forms to process your
  sales? What happens when the printer dies, or you're simply out of ink?

• Your credit card processing equipment. If you take credit card sales, the
  reader might die. (ours did!) Do you know what you would do then? (we
  didn't.)

You get the idea ... there are lots of hidden places where a single failure
can cause major disruption.

It boils down to a risk/cost analysis. It might be cost effective to have a
backup DSL modem for $50 or so, but a spare computer for $2000? Not so much. In
that case, at least understanding that there is risk there might allow you to
build an alternate plan. At my wife's retail store, for example, the plan is
calculators and hand written receipts until I can repair or replace a broken
computer. That's appropriate for her business, your needs might be quite
different.

The most important thing is to simply be aware, and as prepared as you can
be.

Stuff happens.