azure storage

Azure- Optimising BLOB storage

Conor O’Brien
Conor O’Brien
CEO FinAnts North America & Cloud Cost Analyst / Finops

Azure Storage

This Blog focuses on BLOB storage, through the lens of FinOps and cloud cost optimization. Future Blogs will focus on file-based storage and optimization opportunities of this storage type.

For customers running IaaS, behind compute, the largest source of cloud cost and cloud wastage is typically storage. In Azure, storage can be broadly broken down into three categories:

  • Azure BLOB – typically used for backups and to manage general data (individual files can be up to 500TB in Size!)
  • Azure Files – Storage used to host application data – for example, Azure Files would host a Database.
  • Azure Data Lake – Stores complex data typically used for analytics and big data analysis.

Azure BLOB Storage

Azure BLOB storage is used to store unstructured data, typically in very large amounts. BLOBS are organised into containers (no, not like Kubernetes!), and each Azure Account can have an unlimited number of containers. BLOBS must reside in a container. You can purchase Azure BLOB Storage reserved capacity in units of 100 TB and 1 PB per month for a one-year or three-year term. This can provide up to 38% discount off the on-demand rates for some storage tiers.

Azure BLOB Storage Access Tiers

There are 4 tiers of BLOB storage:

  • Premium. This tier is ideal for sensitive applications with high throughput such as online transactions. Uniquely amongst the big 3 public cloud vendors, Azure Premium BLOB storage is based on SSD’s.
  • Hot. This is the default tier and is used for data that is frequently accessed. It is more expensive to store data here, compared to the Cool and Archive tiers, but cheaper to access.
  • Cool. This tier is used for storing less frequently accessed data, such as archived files, backups, and raw or unprocessed data. Cool is designed for data that is likely to be stored for at least 30 days.
  • Archive. This is the most cost-effective option for storing data but is typically more expensive for data retrieval than other tiers. Archive is designed for data that is likely to be stored for at least 180 days, and for systems or scenarios where retrieval latency can be tolerated.
Azure Blob storage
Premium is the costliest per GB stored on it, however the cost to access this data is cheapest. Whereas Archive data is cheapest per GB, but the cost (primarily relating to retrieval time), is highest.
*Adapted from Azure Fridays

Azure BLOB Redundancy

Another big factor that influences BLOB storage costs relates to redundancy. Azure offers 4 different redundancy models. The more replicas and regions, the more it costs.

Azure Blob redundancy

More information about redundancy here.

Azure BLOB Lifecycle Policy

From a cost management perspective, the most important BLOB lifecycle management policies allow a customer to:

  • Transition BLOBS, to a cooler storage tier (hot to cool, hot to archive, or cool to archive) if not accessed or modified for a period of time to optimize for cost.
  • Delete blobs, blob versions, and blob snapshots at the end of their lifecycles.
  • Define rules to be run once per day at the storage account level.

In Conclusion

To make informed decisions about BLOB requirements, comprehensive knowledge of the applications utilising it is needed. Unlike Azure compute resources, the recommendations offered by Azure Adviser can be limited and not much help.

BLOB Storage can make up a significant portion of customer cloud spend and can also be a large component of cloud wastage. There are several factors that customers need to be conscious of to ensure that they are not throwing away money.

Here are some recommendations to reduce and eliminate cloud wastage relating to BLOB storage:

  • Use reservations where possible.
  • Ensure that you use the most appropriate tier of storage based on the applications data requirements.
  • Ensure that you select the most appropriate redundancy based on your business’s requirement – i.e., is Geo-zone-redundant storage (GZRS), which copies your data synchronously across three Azure availability zones, really needed for a Training Systems backup?
  • Implement a BLOB lifecycle policy to transition data to cheaper storage tiers when data access requirements reduce.
  • Plan regular storage reviews with the application owners and adjust.


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