Q. What is Azure Cool storage?
A. Microsoft has introduced a new type of blob storage account which can be configured to use hot or cold storage tiers. These new types of blob storage accounts are different from the regular Azure storage account and conversions between blob and regular storage accounts are not possible. Microsoft has a detailed article at https://azure.microsoft.com/en-us/documentation/articles/storage-blob-storage-tiers/ however the key differences are as follows:
- The SLA for hot it 99.9% while its 99% for cold
- Hot has higher storage costs but lower access and transaction costs compared to the cold tier
The actual performance in terms of IOPS and latency are the same for both hot and cold. The detailed pricing can be found at https://azure.microsoft.com/en-us/pricing/details/storage/ which shows the cold is less than half the storage cost of hot but is around double the access prices. The idea would be to use the cold tier for long term storage of data that is infrequently accessed while using the hot tier for commonly used data. This is different than the Azure Archival Storage which is on the roadmap for very low cost storage that will have delays to access.
The tier of the storage is defined at the account level which means if you need a hot and cold tier you would create two separate blob storage accounts. Additionally you cannot use this storage for virtual disks used by Azure IaaS as they use page blobs which are not available with the blob storage accounts.