Overselling or why my website is slow periodically
What is overselling
Overselling is when a hosting provider sells more resources of a server computer than the computer actually has.
For example, if a server computer has a 1 TB hard-drive, that same hard-drive is sold to 15 customers, while the hosting plan of each of the customers includes 100 Gb disc space. Thus, 1 TB is sold as 1.5 TB.
How is this possible
This is actually possible due to the fact that statistically an average hosting client uses about 50% of the resources of the purchased hosting plan. I.e. 5 Gb out 10 GB ordered.
Overselling allows a hosting provider to optimize expenses and generate more income out of available assets.
Overselling is bad for the customer
Generally, the customer is the one that suffers from the hosting provider's overselling policy. It is possible to oversell not only disc space, but CPU time, or bandwidth or memory. In such a case, during peak activity of all the websites hosted on a server the server will simply have less resources than it needs which will result in slow connectivity, response time, server failure and websites unavailabilty.
Webhosting solutions that are most often oversold
Typically, shared hosting is the #1 web-hosting service that is oversold by the hosting provider. It is also possible to use overselling when offering virtual private servers based on certain technologies, such as openVZ, for example.
Should you notice your website is down or slow everyday at certain times, the reason might be overselling by the provider.