Bandwidth and Server Load, What's That?

Written by: Niche Content - Sep 5, 2008

Two key performance metrics will impact every web site owner sooner or later: bandwidth and server load.

Bandwidth is the amount of network capacity available, and the term actually covers two different aspects. 'Bandwidth' can mean the measure of network capacity for web traffic back and forth at a given time. Or, it sometimes is used to mean the amount that is allowed for some interval, such as one month. Both are important.

As files are transferred, emails sent and received, and web pages accessed, network bandwidth is being used. If you want to send water through a pipe, you have to have a pipe. Those pipes can vary in size and the amount of water going through them at any time can also vary.

Total monthly bandwidth is a cap that hosting companies place on sites in order to share fairly a limited resource. Companies monitor sites in order to keep one site from accidentally or deliberately consuming all the network capacity. Similar considerations apply to instantaneous bandwidth, though companies usually have such large network 'pipes' that it's much less common for heavy use by one user to be a problem.

Server load is a more generic concept.

It often refers, in more technical discussions, solely to CPU utilization. The CPU (central processing unit) is the component in a computer that processes instructions from programs, ordering memory to be used a certain way, moving files from one place to the next and more.

Every function you perform consumes some CPU and its role is so central (hence the name) that it has come to be used as a synonym for the computer itself. People point to their case and say 'That is the CPU'. But, the computer actually has memory, disk drive(s) and several other features required in order to do its job.

Server load refers, in more general circumstances, to the amount of use of each of those other components in total.

Disk drives can be busy fetching files which they do in pieces, which are then assembled in memory and presented on the monitor, all controlled by instructions managed by the CPU.

Memory capacity is limited. It's often the case that not all programs can use as much as they need at the same time. Special operating system routines control who gets how much, when and for how long, sharing the total 'pool' among competing processes.

So, how 'loaded' the server is at any given time or over time is a matter of how heavily used any one, or all, of these components are.

Why should you care?

Because every web site owner will want to understand why a server becomes slow or unresponsive, and be able to optimize their use of it.

When you share a server with other sites, which is extremely common, the traffic other sites receive creates load on the server that can affect your site. There's a limited amount you can do to influence that situation. But if you're aware of it, you can request the company move you to a less heavily loaded server. Or, if the other site (which you generally have no visibility to) is misbehaving, it's possible to get them moved or banned.

But when you have a dedicated server, you have much more control over load issues. You can optimize your own site's HTML pages and programs, tune a database and carry out other activities that maximize throughput. Your users will see that as quicker page accesses and a more enjoyable user experience.