What is Blob Storage

Blob storage accounts are specialized storage accounts for storing your unstructured data as blobs in Azure Storage. In azure previously there has been only one kind of storage account which is called General Purpose Storage account. It provides conventional storage for blobs, files, tables and queues. Azure recently introduced a new storage account called Blob Storage. Microsoft is repeating the gambit in the storage world with the introduction of new archiving service for protecting infrequently used records.

The catch is that cool blob storage model is geared towards information is accessed less than once in a month. Common scenarios for cool storage are backup data, disaster recovery, media content,   social media videos and images, Auditing data etc. Consumers will see the best cost savings by using the cool storage for appropriate datasets.

Data is growing exponentially in today’s world. So the only way managing the cost for your storage is tiering your data based on how often the data is accessed.


This is where Azure Blob Storage comes into the picture.

Access Tier (Cool/Hot)

The access tiers available for blob storage accounts are Hot/Cool. Access tier attribute of hot/cool is set at an account level and applies to all the objects in that account. So it is not possible to have single storage account which serves the both purposes. If you need both, you will need to create two accounts. If there is any change in the usage pattern you can switch between the Access Tiers.

Comparison between Hot and Cool Access Tier:


Microsoft is guaranteeing slightly higher availability on its hot access tier of 99.9% compared with 99% availability guarantee for cool access.

This new account supports various replication options

  • Locally Redundant Storage (LRS)
  • Geo-Redundant Storage (GRS)
  • Read-Access Geo-Redundant Storage(RA-GRS)


There are different costs involved such as storage costs, data access costs, transaction costs, replication costs, out bound data transfer costs and changing the access tier costs. For more than 5000 TB/Month contact Microsoft Support.


Migrating existing data to Cool Blob Storage

Below are the tools used for migrating data.


It is the command line utility designed for copy of data to and from Azure storage.By default, AzCopy is installed to %ProgramFiles(x86)%\Microsoft SDKs\Azure\AzCopy (64-bit Windows) or %ProgramFiles%\Microsoft SDKs\Azure\AzCopy (32-bit Windows).

Ex 1: Copy data from local to Cloud Storage

AzCopy /source:C:\CoolData /dest: https://coolblob.blob.core.windows.net/coolcontainer /destkey:”access key” /s

  • Azcopy =  Executable
  • /Source = the local folder
  • /Dest = the blob container
  • /Destkey = the blob access key
  • /s = copies the directory structure

Ex 2: Copy blobs within storage accounts,

  • AzCopy /Source:https://myaccount.blob.core.windows.net/mycontainer1 /Dest:https://myaccount.blob.core.windows.net/mycontainer2 /SourceKey:key /DestKey:key /Pattern:abc.txt

Ex 3: Across storage accounts

  • AzCopy /Source:https://sourceaccount.blob.core.windows.net/mycontainer1 /Dest:https://destaccount.blob.core.windows.net/mycontainer2 /SourceKey:key1 /DestKey:key2 /Pattern:x*.txt

More information is available here

REST API/Client Library:

Create a custom application to migrate data into a Blob storage account using one of the Azure client libraries or the Azure storage services REST API.

Key Points Blob Storage

  • Existing applications do not have the ability to choose an access tier.
  • Right now there is no option for converting the existing storage account to Blob storage account. Migration is the only way by creating new storage account with cool Tier.
  • Blob storage account supports only block and append blobs and not page blobs. Azure VMs are stored in the form of Page Blobs as a result we cannot store this.


                Azure cool storage tier is optimized for storing data that is frequently accessed and long lived. Existing storage accounts cannot be converted to Blob storage account, migration can help us in doing this. There is no big difference from consumer point of time while accessing the data. Going forward Cool Blob storage is the recommended way for storing the data.