Web Hosting: Overselling vs. Overloading

When looking for a web host, a common advice you’ll get from other people is, “make sure your host doesn’t oversell.” Is overselling really bad? Is it any different than overloading, or are they the same thing? Just how correct is this advice?

Web Server Overselling

Here’s an explanation of overselling from Web Hosting Talk’s wiki:

Overselling is where a web hosting provider has (for example) 100GB space and 1000GB data transfer on their server. They sell 150 accounts, each with 1GB space and 10GB data transfer. To some people, this level of overselling is acceptable. It’s unlikely that even 100 of the accounts will use their 1GB. The bandwidth is usually a burstable limit, so even if it is reached, the server won’t suddenly go offline. More likely, the web host will have to pay the datacenter some overage. There are sufficient resources to provide the service, and the host will probably have the foresight to upgrade the servers as needed.

Wiki article permalink

As detailed above, it just means that the web host continues to put accounts on a server while it still has available resources. The keyword here is “available.”

Overselling doesn’t automatically mean there are 200 full accounts stuffed on a server which can only handle a maximum of 100 full accounts! There may be 200 accounts, but most of these accounts could be using just 1% of the maximum amount of resources they can use so it’s all good.

Web Server Overloading

Overloading happens when a server is experiencing excessive load and the server’s overall performance is degraded. This could happen when there’s simply too much accounts and they’re all using 100% of their available resources. For example, 200 resource-heavy accounts on a server which can only handle 100 accounts. This could also happen when there’s a server hog — an account or website that’s placing too much load on the server (very common in “unlimited” hosting).

Overloading affects all the websites on the same server, so everyone suffers from the same consequences regardless if your site is the one using up resources or not.

A server overload and performance degradation won’t happen if there’s an ample amount of available resources on a server. So again, the keyword here is “available.”

So, is overselling okay?

It’s perfectly fine if your host oversells. Assuming that every one of their clients would surely consume 100% of the allocated resources is just not practical at all.

Here’s a fact: Most web hosting clients won’t ever max out their resource allocation. So for a host to have to purchase and setup a new server — even when there’s one that’s just 20% filled — is simply bad for their business. If they do this then they might have to increase their monthly fees to cover the costs, and we don’t want that!

Overselling helps web hosts keep their costs low so let them do it. A good host will know when they need new servers (or upgrades) anyway. So when choosing a host, your requirement must not be simply “a host who isn’t overselling.” What you want to make sure is that they are proactive in monitoring their servers so that overloading doesn’t happen.