The difference between bandwidth and data transfer
It is very common to find the two words – bandwidth and data transfer, used synonymously on the internet, specially on web host’s pricing plans. However, technically speaking, there is quite a difference between these two terms. Bandwidth denotes the volume of data that can be transferred per unit of time. Data transfer is the measure of the traffic generated from your website. The difference is that the bandwidth is a rate of data transfer.
If the bandwidth is high, the website will load faster because it can transfer more data per second. This does not mean that the data transfer will be high, because the amount of data transferred will depend on the number of visitors to your website and the file sizes of your website pages (including image, audio and video files etc.). The greater the number of visitors, the greater the amount of data transferred from your website, and so larger will be the data transfer.
Bandwidth and connection to internet
Bandwidth is usually expressed in bits per second (bps) or bytes per second. It is a very important measure of an input output (I/O) device. For example the modem that we use to connect to the internet has a certain maximum bandwidth (say 56 Kbps). On the other side a cable modem can transfer more data per second and usually has a bandwidth of around 200 – 1000 Kbps. A T1 line to the internet can transfer at the rate of 1.5 Mbps or higher.
Data transfer requirements for websites
Data transfer is measured in bytes, kilo bytes (KB), mega bytes (MB) or giga bytes (GB). If a website delivers 100,000 pages each month with average page file size of 20 KB, the data transfer per month will be 2 GB. Almost 80% of websites on the internet uses less than 5 GB of data transfer per month.
30 Gigabytes of monthly bandwidth or data transfer translates to about 30,000 unique visitors per day. The average website uses less than 250MB of bandwidth per month and receives about 50 visitors per day, so only very popular sites ever exceed 30GB.
Truths about unlimited data transfer
Some web hosts claim that they offer unlimited or unmetered data transfer. Higher bandwidth cost money and tie up server resources, so if any host truly offered unlimited data transfer at any price they would not be in business for very long. If you read their Terms of Service, you will find the following language or something similar:
“If at any time the Customer’s website generates enough bandwidth usage to affect the performance of other customer sites on the server, we reserve the full right to terminate the Customer’s domain name without refund.”
What this means is if the host feels that any customer’s website is costing them more money in bandwidth than the amount that customer pays, they will close the account without refund. Of course the resources of each server are set up not to exceed a certain amount of traffic, so higher bandwidth usage by any customer will automatically have an impact on other accounts on that server. The big question is what kind of bandwidth do they consider excessive, 1GB, 2GB, 3GB, 5GB, etc.? Is their bandwidth really unlimited or unmetered? If they do not measure bandwidth, how would they know when someone is using too much, and how can they keep their servers from running out of resources?
Sourced from http://content.websitegear.com