What is a Server Anyways

The other day I was talking to somebody who mentioned they didn't even fully understand what a server is and what it does, and this was coming from somebody that I consider to be fairly technical. So let's cover what a server actually is. Here's a hint: a physical server, this piece of hardware, I wouldn't consider even the most important part of what a server is.

What a server does

A server is an important part of today's technology. A server delivers different services to us. We would request a service, and then the server would deliver that service to us. As an example, if I were to go to a restaurant, a server would come and take my order, they would then submit that order to the cook, and once my food was prepared, they would deliver that food to my table. They're performing a service for me. Similarly, this server would deliver services for me. I would set this up to deliver certain services.

I look at a server as being three layers. There is the physical layer, there's the operating system, and then there is the application that's actually delivering the services, the program that's actually delivering the services to me. We're going to start out by talking about the application, because the application is the most important part; that's what's actually delivering the services to us. Then we're going to briefly mention the operating system that goes on this, and what the differences are between the operating system of a server and a regular client. And then we're going to get into the physical equipment and what makes this different than a regular computer.

The client-server relationship and the application

Here on the right side we have some servers, and they are going to provide services for a client; this is why this is called a client-server relationship. This client will request some sort of services from the server, and then those servers will deliver that service. So what could these services look like? One might be DHCP: this machine needs an IP address, and perhaps it's requesting an IP address from the servers. Or maybe it's trying to resolve a domain name, that's DNS services. Or perhaps it's requesting a web page, so there are web services being delivered.

On this client machine we would find some sort of software that's making that request, and on the server we would find some sort of software that is responding to that request. If this user is trying to access a website, they're going to open up a browser, something like Firefox, Safari, Edge, or Chrome, and that browser is the client app. That client app is going to make a request, and it's going to go to the server, and the server is going to respond, and it's running some sort of server app, something like Apache, which is website services, and that's what's going to be delivering the website to the client.

On your Windows machine, you can open up Windows and type in services. This is going to show a list of different software that's running on your computer. One of the examples I gave was the DHCP service; here is the DHCP client, that's the app running on this machine that's requesting DHCP services. If I were to go to the server that's providing DHCP services, I would see a DHCP server. Similarly, we can see there is a DNS client on here. So really, the key to this client-server relationship is the client software that's making the request and the server software that's responding to that request.

Why separate hardware and operating systems

If that's the case, why do we have separate hardware, and why do we have a separate operating system? I could actually take Apache, which delivers web pages, and install that on any machine and get it up and running. So why would I want separate physical hardware? This is specialized; this is to deliver certain services in a more efficient manner.

Let's take a look at the services console of this Windows machine. If I look through this, these are all the applications running on this machine, and we can see things like this DHCP client and the DNS client, which I pointed out earlier, but we see a lot of other software. Realize that this is a Windows machine; it's really designed for end users to interact with, and so a lot of the software running on here is to create a very positive experience for those end users. But it does slow down your computer some, and it can cause some problems and conflict issues. When you're talking about a server operating system, something like Microsoft server, you will find that the base programming is actually very similar, but the services that are running can vary quite a bit. A lot of the services running on this client operating system you will not find on a server operating system, and vice versa. They're really tuned for what they're designed to do, so the server operating system is really streamlined to provide services in that client-server relationship.

The hardware

Same thing is true for the hardware side of things. One of the first things you may notice is that we have a very thin profile and it's very long, and this is designed to put on a rack with a lot of other servers. Not all servers are set up this way, but a lot of them are rack mountable, so they're meant to be on racks with lots and lots of other servers, and it streamlines even the cooling and all the power and all of the components to be uniform with other servers.

Another thing you may notice is there's a lot of duplicate stuff on here. These are each fans, so we have many different fans on here. We've got multiple CPUs, multiple power supplies. Here are the hard drives; there's a spot for eight different hard drives, and a lot of these things are hot swappable, so I could actually take a drive out while this is running and it would still be up and running. Or I could take the power out of one of these and this would still be up and running because I have another power supply. So there's a lot of redundancy built in with this.

The components in here are also more robust. Hard drives are usually built a little more robust than your standard components, the processors are a little more robust; the hardware on here is really meant for being up and running all the time with no breaks, so you get a lot more longevity out of the components of the server. Not only are the components usually a little more robust and able to handle a little bit more, but they can also operate at a higher level. The input/outputs on our hard drives tend to be much faster; we use RAID controllers for those hard drives so we can stripe across many disks and get more speed out of them. We have Xeon processors, which can handle a lot of threads all at once and do a lot of processing all at once. We have 24 DIMM slots here with a total of 1.5 terabytes of memory that we could put into here. That's just, and this is an older server too, so we can put a lot of memory into these. The network interface cards operate at 10 gig speed, so they're much faster.

We also have a special interface back here. On this particular one, since this is a Dell server, this is an iDRAC, and we can manage this server. I could connect to this server through this interface through Ethernet and control all aspects of the server even when it's turned off. I could actually get onto the server and turn it on. You really just can't do that with any kind of desktop machine; you have to have it on before you can even remote into it, whereas this machine you can remote into even when it's off. So a lot of control there.

Server limitations

It does have some limitations. For instance, usually your server doesn't really need to have a lot of graphical calculations going on with it, so this doesn't really have a high GPU. We could put something in here, but there's really not even space for a good GPU card, so we don't have good GPU processing with it. There are not a lot of expansion slots with it, because it's not designed for the expansion of this machine. So there are some limitations, but as you can see, there's a lot of cool stuff that they cram into this little space.

As you can see, it's not necessarily a real simple answer of what a server is, because really, when you render it down, it's that application that provides a service to the end user, but we have an operating system and hardware that's specifically tuned to help provide excellent services to our end users. It's one of the reasons why I really love this IT industry and my career and what I've got to experience, because you get to play with cool tools like this and set up servers that have terabytes of memory inside of them to deliver awesome services that people can get from around the world. It's still quite amazing to me.