Q. What is a Cool Azure Storage Account?
A. There are now two different types of storage account in Azure: General purpose and Blob storage. General purpose accounts support all the different types of storage services such as all types of blobs, files, tables and queues. Blob storage is a new type of storage account that has two different types of access tier which can be hot or cool. Blob storage accounts only support block blobs and append blobs and not page blobs (i.e. VHDs).
While both hot and cool tiers have the same durability and response times they are billed differently and cool has a slightly lower SLA. Essentially cool is less than half the cost of the equivalent hot tier for the data storage while the operation costs (access and transaction) on the cool tier is around double that have the hot tier. What this means is cool is suited for storing large amounts of data that is infrequently accessed while the hot tier is better suited for data that is accessed more frequently.