-: To ensure our systems remain online,
we need to ensure that they have redundant power.
Now, there are a lot of different ways
to do this, but let's begin with
the idea of a redundant power supply.
A redundant power supply is simply an enclosure
that provides two or more complete power supplies
inside of one.
You learned about this back in your A plus studies.
Now, most servers are going to utilize
two individual power supplies in the servers case
to ensure that power is always available
to that server at all times.
This eliminates a single point of failure
that really does exist inside your desktop computer.
If you look in your desktop computer,
you only have a single power supply.
If it fails, the entire computer
is going to fail with it.
But, with servers, we have two power supplies,
those redundant power supplies.
And, so, this is going to ensure
that we can mitigate the threat
of power supplies failing on us
and taking down the entire server or system.
Now, speaking of power, for the security plus exam,
you need to know a few conditions that describe
the various issues that can be involved
with a power source.
These include things like surges,
spikes, sags, brownouts, and blackouts.
Again, you learned all of these back in A plus,
so we're just going to do a quick review here.
First, let's cover a surge.
A surge in electrical means that there is
an unexpected increase in the amount
of voltage that's being provided.
So here in the United States,
our power supply is 120 volts.
If that went up to, say, 124 or 125 volts,
that's only a little bit of an increase in power.
So that would be considered a surge.
Now, if it jumped up a lot,
then we would have what we call a spike.
Now, a spike is going to be a short transient voltage
that's going to be due to a short circuit,
a tripped circuit breaker, a power outage,
or even a lightning strike.
This might jump from 120 volt up to
maybe 140 or 150, or even more.
Now, to protect against a surge or a spike,
you should use a surge protector.
A surge protector is going to help you
against those little surges, but if you have
a really good surge protector, it can help
when you have those large spikes as well.
Now, the next thing we're going to talk about is a sag.
A sag is kind of like a surge, but in reverse.
Where a surge went up, a sag is an unexpected decrease
in the amount of voltage provided.
So it's going to go down.
Typically, sags are only for a short duration
of time, and usually it's not even going to
make the power get lost to your computers.
However, when that voltage reduces for longer
than that, it becomes known as a brownout.
A brownout is when a voltage drops
to such an extent, that usually your lights
start dimming and your computer would even shut off.
So, if I'm used to 120 volts,
maybe I'm going to have a brownout where
I drop down to 90, or 80, or 70 volts,
and that's not enough power to keep
the computer running, and so we're going to lose power.
Finally, we have a blackout.
Now, a blackout occurs when there is
a total loss of power for a long period of time.
So, if you're sitting in your house
and the lights all go out and the computers turn off
and it happens for 30 seconds or a minute,
that's considered a prolong amount of time
for a blackout.
Now, another problem associated with these blackouts,
is often when they come back from those blackout conditions,
you get a spike in power that occurs,
and this can damage your computers as well.
Again, this is why those surge protectors
are really important.
In the next lesson, we're going to discuss how
we can protect ourselves form all
of these conditions using proper backup power
and line conditioning.