Azure Storage - Retention Type

In Azure Blob Storage, data can be stored in three different access tiers, each representing different levels of access frequency, retrieval speed, and cost: Hot, Cool, and Archive. Below is a description of each:

1. Hot Access Tier:

• Usage: Optimized for storing data that is accessed frequently.

• Cost: Higher storage costs compared to Cool and Archive tiers, but lower access costs.

• Retrival Time: milliseconds

• Best for: Data that is frequently read and modified, such as a database's active dataset or the temporary storage for a processing job.

2. Cool Access Tier:

• Usage: Optimized for storing data that is infrequently accessed and stored for at least 30 days.

• Cost: Lower storage costs compared to the Hot tier, but higher access costs.

• Retrival Time: milliseconds

• Best for: Data that is infrequently accessed, such as backup, logging, and telemetry data that is kept for operational reasons but accessed less frequently.

3. Archive Access Tier:

• Usage: Optimized for storing data that is rarely accessed and stored for at least 180 days.

• Cost: Lowest storage costs but the highest access costs.

• Retrieval Time: Data retrieval times can be up to 15 hours, making it unsuitable for data that needs to be readily available.

• Best for: Long-term retention of data that is seldom or never accessed, such as compliance and archival data.

Transitioning Between Tiers:

• Automated Transitioning: Policies can be set up to automatically transition blobs between different access tiers based on the age of the blob.

• Manual Transitioning: Users can also manually change the access tier of a blob at any time.

Immutable Storage:

• For legal and compliance needs, the Archive tier can be coupled with Immutable Blob Storage, which allows users to create Write Once, Read Many (WORM) protected instances of blob data, preventing them from being modified or deleted for a specified retention interval.

source: https://learn.microsoft.com/en-us/azure/storage/blobs/access-tiers-overview