Fault Management

00:00

let's switch gears a little bit and start talking about what happens when things go bad for good. Network admins.

00:07

Regardless of what incidents happen on the network, all management and fault tolerance is always going to be essential.

00:13

When we talk about fault management, we're really talking about being able to withstand failures of one or multiple devices and continue to move forward.

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Do we have the redundancy in place? Do we have the capabilities to keep moving forward as an organization?

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At first, when we're planning for redundancy, we have to have some idea of how much redundancy we need.

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How much is enough?

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There are a couple of terms, a couple of metrics that might be helpful.

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The first is a key performance indicator.

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K P.

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The key performance indicator will give us an idea of whether or not a device is performing to its expectations, because rarely does the device just stop working.

00:52

Often service starts to agreed, and we start to see some issues come up

00:56

of a specific device isn't meaning. It's standard performance. That might be an indicator that we're looking at a device that's getting ready to fail.

01:03

There are also metrics that the vendors give to us.

01:07

One is meantime, to fail in mean time between failures.

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These are pretty comparable. But the idea is meantime, to fail indicates this is a device that we don't repair.

01:19

This is the lifespan of the device. We're going to buy it. Three years later, it's going to fail.

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Mean time between failures gives the indication that the device can be repaired.

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We buy the device, it goes three years. It fails, we prepare it. Three years later, it fails, we repair it, and so on.

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Then we've also got to consider how long it takes us to prepare the device, which is mean time to repair.

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If it's going to take us a long time to repair that device, is it possible that we can just replace it?

01:49

A lot of these we don't really repair a whole lot of devices today because most of them can be replaced much cheaper than the time and effort it would take to prepare them.

01:57

The last our service level agreements,

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vendors are going to provide us with commitments as to performance and availability.

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A lot of times that revolves around up time.

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For instance, if I'm storing my data with the cloud service provider. The redundancy is up to them, so that way they can meet their metrics

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with redundancy. We want a redundancy to be comprehensive and not just focus on just redundant data or just redundant drives.

02:24

We really want to make sure that all of our areas are redundant because the chain is only as strong as the weakest link.

02:30

We start off by talking about redundancy and servers.

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That's just multiple servers performing the same role.

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This is not the same as a cluster because with redundant servers,

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each server is its own unique device.

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I have domain controller A and domain controller B or a DNS one DNS, too.

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If one fails, the second is up and running and is available

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A cluster. I have multiple physical nodes acting as a single logical entity.

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They are very tightly coupled.

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For instance, if I have a cluster or a server farm, as you sometimes hear them, you're not going to be able to different entry between the servers.

03:10

When I go to amazon dot com, there are many hundreds or machines responding to Web series.

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I don't know which one is which, because they are functioning as part of the same cluster

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clusters also usually do provide load balancing.

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But you can also have clusters that don't load balance.

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They're just simply working for fault tolerance

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in a smaller environment. I might have multiple servers.

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They could either both be responding to requests, or one could be passive, while the other is the primary responding server.

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There are all sorts of configurations. The real purpose and the real important piece is that we need our fault tolerance for those servers.

03:47

That's where services run.

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That's where our resources are.

03:51

Many times we spare equipment.

03:53

I was switching the closet and we talk about cold spares. That's exactly it.

03:58

I got a device somewhere in the closet.

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I can find it. I can stall it.

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We often have warm spares, which are ready to go very quickly.

04:08

Hotspots or hot spares are already installed in just matter, switching over to them,