Guaranteed RAM and Burstable RAM both are a common term in web hosting servers. Many hosting companies offer Guaranteed RAM in their dedicated servers while in affordable Virtual Private or Shared servers Burstable RAM is offered for any sudden load increase on the webservers.
Guaranteed RAM is the amount of constantly available physical memory, which is stated in your account quota. Whereas, Burstable RAM is the amount of physical memory, available on a temporary basis for load spikes.
These days, due to healthy competition, almost all the hosting companies are offering Dedicated RAM even on the small dedicated, or virtual private resources. So the concept of Burstable RAM is vanishing. But it still exists in the shared server environment to combat instant spikes in the overall load caused by any uncommon events.
Here is small comparison between the Guaranteed and Burstable RAM.
|Guaranteed RAM||Burstable RAM|
|An amount of memory is dedicated to the server.||A certain amount of memory is dedicated, and more shared memory is available in case of a sudden load.|
|Guaranteed RAM is not shared with any other.||Burstable RAM is shared with all the clients available on the same server in a virtualized manner.|
|Since there is no software to isolate your server with others, latency is the lowest because of the dedicated resource environment.||Due to server management software like cPanel or WHM, latency may suffer if other peer clients use more resources along with you.|
|Under small load performance is excellent. Even with heavy load performance is good due to no sharing.||Under small load performance is good. But under heavy load the performance is average, and you can not use that extra boost for a longer time.|
|The cost of such servers is usually high.||The cost of such servers is affordable.|