-: In the last lesson I showed you a couple of diagrams 2 2
of redundant networks, 3 3
but one of the things we had to think about in this lesson 4 4
are the considerations we have 5 5
when we start designing these redundant networks. 6 6
First you need to ask yourself, 7 7
are you going to use redundancy in the network, 8 8
and if so, where, and how? 9 9
So are you going to do it from a module or a parts perspective? 10 10
For instance, are you going to have multiple power supplies, 11 11
multiple network interface devices, multiple hard drives, 12 12
or are you going to look at it more from a chassis redundancy 13 13
and have two sets of routers or two sets of switches? 14 14
These are things you have to think about. 15 15
Which one of these are you going to use, 16 16
because each one is going to affect the cost 17 17
of your network, based on the decisions you make. 18 18
You have to be able to make a good business case 19 19
for which one you're going to use, and why. 20 20
For instance, if you could just have 21 21
a second network interface card or a second power supply, 22 22
that's going to be a lot cheaper 23 23
than having to have an entire switch 24 24
or an entire extra router there. 25 25
Now, each of those switches and routers, 26 26
some of these can cost 3 or 4 or $5,000, 27 27
and so it might be a lot cheaper 28 28
to have a redundant power supply, right, 29 29
and so these are the things you have to think about 30 30
and weigh as you're building your networks. 31 31
Another thing you have to think about 32 32
is software redundancy, 33 33
and which features of those are going to be appropriate. 34 34
Sometimes you can solve a lot of these redundancy problems 35 35
by using software as opposed to hardware. 36 36
For example, if you have a virtual network setup, 37 37
you could just put in a virtual switch 38 38
or a virtual router in there, 39 39
and that way you don't have to bring 40 40
another real router or real switch in, 41 41
that can save you a lot of money. 42 42
There's also a lot of other software solutions out there, 43 43
like a software RAID, 44 44
that will give you additional redundancy 45 45
for your storage devices, 46 46
as opposed to putting in an extra hard drive chassis, 47 47
or another RAID array or storage area network. 48 48
Also, these are the types of things 49 49
you have to be thinking about 50 50
as you're building out your network, right? 51 51
When you think about your protocols, 52 52
what protocol characteristics 53 53
are going to affect your design requirements? 54 54
This is really important if you're designing things, 55 55
and you're using something like 56 56
TCP versus UDP in your designs, 57 57
because TCP has that additional redundancy 58 58
by resending packets, where UDP doesn't, 59 59
this is something you have to consider as well. 60 60
As you design all these different things, 61 61
all of these different factors are going to work together, 62 62
just like gears, and each one turns another, 63 63
and each one is going to feed another one, 64 64
and the more reliability and availability 65 65
you get in your networks 66 66
by adding all these components together. 67 67
In addition to all this, 68 68
there are other design considerations 69 69
that we have to think about as well, 70 70
like what redundancy features should we use 71 71
in terms of powering the infrastructure devices? 72 72
Are we going to have internal power supplies 73 73
and have two of those, and have them redundant? 74 74
Or, are we going to have battery backups, or UPSs, 75 75
are we going to have generators? 76 76
All of these things are things you have to think about, 77 77
and I don't have necessarily the right answers for you, 78 78
because it all comes down to a case-by-case basis. 79 79
Every network is going to be different, 80 80
and every one has its own needs 81 81
and its own business case associated with it. 82 82
The network that I had at former employers 83 83
were serving hundreds of thousands of clients, 84 84
and those were vastly different than the ones 85 85
that are servicing my training company right now, 86 86
with just a handful of employees. 87 87
Because when you're dealing with your network design 88 88
and your redundancies, 89 89
you have to think about the business case first. 90 90
Each one is going to be different 91 91
based on your needs and your considerations. 92 92
What redundancy features should be used 93 93
to maintain the environmental conditions of your space? 94 94
If you have good power and space and cooling, 95 95
you need to make sure 96 96
that you're thinking about air conditioning, 97 97
and do you have one unit or two? 98 98
Do you have generators onsite? 99 99
Do you have additional thermal heating or thermal cooling? 100 100
All of these things are things you have to think about. 101 101
What do you do when power goes down? 102 102
What are some of those things 103 103
that you're going to have to deal with 104 104
if you're running a server farm 105 105
that has to have units running all the time, 106 106
because it can't afford to go down 107 107
because it's going to affect 108 108
thousands and thousands of people, 109 109
instead of just your one office with 20 people? 110 110
All of these are things you have to consider 111 111
as you think about it. 112 112
In my office, we made the decision 113 113
that one air conditioning unit was enough, 114 114
because if it goes down, we might just not work today 115 115
and we'll come to work tomorrow, we can get over that. 116 116
But in a server farm, 117 117
we need to make sure we have multiple air conditioners, 118 118
because if that goes down 119 119
it can actually burn up all the components, right? 120 120
So we have to have additional power and space and cooling 121 121
that are fully redundant, 122 122
because of that server infrastructure 123 123
that we're supporting there. 124 124
These are the things you have to balance in your practices. 125 125
And so when you start looking at the best practices, 126 126
I want you to examine your technical goals 127 127
and your operational goals. 128 128
Now what I mean by that is, 129 129
what is the function of this network? 130 130
What are you actually trying to accomplish? 131 131
Are you trying to get to 90% uptime, or 95%, or 99%, 132 132
or are you going for that gold standard 133 133
of five nines of availability? 134 134
Every company has a different technical goal, 135 135
and that technical goal is going to determine 136 136
the design of your network. 137 137
And you need to identify that 138 138
inside of your budgeting as well, 139 139
because funding these high-availability features 140 140
is really expensive. 141 141
As I said, if I want to put a second router in there, 142 142
that might cost me another 3,000 or $5,000. 143 143
In my own personal network, 144 144
we have a file server, and it's a small NAS device. 145 145
We're not comfortable just having all of our devices there, 146 146
so we decided we weren't comfortable 147 147
having all of our file storage on a single hard drive, 148 148
and we built this NAS array instead, 149 149
so if one of those drives goes out, 150 150
we have three others that are carrying the load. 151 151
This is the idea here. 152 152
Now, eventually we decided we didn't need that NAS anymore, 153 153
and so we replaced that NAS enclosure with a full RAID 5. 154 154
Later on we took that full RAID 5 155 155
and we switched it over to a cloud server 156 156
that has redundant backups 157 157
in two different cloud environments. 158 158
And so all of these things work together 159 159
based on our decisions, 160 160
but as we moved up that scale 161 161
and got more and more redundancy, 162 162
we have more and more costs associated. 163 163
It was a lot cheaper just to have an 8-terabyte hard drive 164 164
with all of our files on it, 165 165
then we went to a NAS array 166 166
and that cost two or three times that money, 167 167
then we went to a full RAID 5 168 168
and that cost a couple more times that, 169 169
then we went to the cloud and we have to pay more for that. 170 170
Remember, all your decisions here 171 171
are going to cost you more money, 172 172
but if it's worth it to you, that would be important, right, 173 173
and so these are the things you have to balance 174 174
as you're designing these fully redundant networks, 175 175
based on those technical goals. 176 176
You also need to categorize 177 177
all of your business applications into profiles, 178 178
to help with this redundancy mission 179 179
that you're trying to go and accomplish here. 180 180
This will really help you as you start 181 181
going into the quality of service as well. 182 182
Now if I said, for instance, 183 183
that web is considered category one 184 184
and email is category two 185 185
and streaming video's going to be category three, 186 186
then we can apply profiles 187 187
and give certain levels of service 188 188
to each of those categories. 189 189
Now we'll talk specifically of how that works 190 190
when we talk about quality of service in a future lesson. 191 191
Another thing we want to do 192 192
is establish performance standards 193 193
for our high-availability networks. 194 194
What are the standards that we're going to have to have? 195 195
These standards are going to drive 196 196
how success is measured for us, 197 197
and in the case of my file server, for instance, 198 198
we measure success as it being up and available 199 199
when my video editors need to access it, 200 200
and that they don't lose data, 201 201
because if we lost all of our files, 202 202
that'd be bad for us, right? 203 203
Those are two metrics that we have, 204 204
and we have numbers associated with each of those things. 205 205
In other organizations, we measure it based on the uptime 206 206
of the entire end-to-end service, 207 207
so if a client can't get out to the internet for an ISP, 208 208
that would be a bad thing, that's one of their measurements. 209 209
Now the other one might be, what is their uptime? 210 210
All of these performance standards are developed 211 211
through metrics and key performance indicators. 212 212
If you're using something like ITIL 213 213
as your IT service management standards, 214 214
this is what you're going to be doing as you're trying 215 215
to run those inside your organization as well. 216 216
Finally, here we wanted to find how we manage and measure 217 217
the high-availability solutions for ourselves. 218 218
Metrics are going to be really useful to quantify success, 219 219
if you develop those metrics correctly. 220 220
Decision-makers and leaders love seeing metrics. 221 221
They love seeing charts and seeing the performance, 222 222
and how it's going up over time, 223 223
and how our availability is going up, 224 224
and how our costs are going down. 225 225
Those are all good things, 226 226
but if you don't know what you're measuring 227 227
or why you're measuring it, 228 228
it really goes back to your performance standards. 229 229
Then, these are the kind of things 230 230
that are wasting your time with metrics. 231 231
A lot of people measure a lot of things, 232 232
and they don't really tell you 233 233
if you're getting the outcome you're wanting. 234 234
I want to make sure that you think about 235 235
how you decide on what metrics you're going to use. 236 236
Now, we've covered a lot of different design criteria 237 237
in this lesson, but the real big takeaway here 238 238
that I want you to think about is this. 239 239
If you have an existing network, 240 240
you can add availability to it, 241 241
and you can add redundancy to it. 242 242
You can retrofit stuff in, 243 243
but it's going to cost you a lot more time 244 244
and a lot more money. 245 245
It is much, much cheaper 246 246
to design this stuff early in the process 247 247
when you start building a network from scratch. 248 248
So, if you're designing a network and you're asked early on 249 249
what kind of things you need, 250 250
I want you to think about all these things of redundancy 251 251
in your initial design. 252 252
Adding them in early is going to save you a lot of money. 253 253
Every project has three main factors, 254 254
time, cost, and quality, 255 255
and usually, one of these things is going to suffer 256 256
at the expense of the other two. 257 257
For example, if I asked you to build me a network 258 258
and I want it to be fully redundant 259 259
and available by tomorrow, could you do it? 260 260
Well, maybe, but it's probably going to cost me a lot of money, 261 261
and because they give you very little time, 262 262
it's going to cost me even more, 263 263
or your quality is going to suffer. 264 264
So, you could do it good, you could do it quick, 265 265
or you could do it cheap, but you can't do all three. 266 266
It's always going to be a trade-off between these three things, 267 267
and I want you to remember 268 268
as you're out there and you're designing networks, 269 269
you need to make sure you're thinking about your redundancy 270 270
and your availability and your reliability, 271 271
because often that quality is going to suffer 272 272
in favor of getting things out quicker 273 273
or getting things out cheaper.