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azure_blob_storage.md

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Azure Blob Storage

Azure Blob Storage is a service that enables you to store massive amounts of unstructured data as binary large objects (i.e. blobs) in the cloud.

Blobs are an efficient way to store data files in a format that is optimized for cloud-based storage and applications can read and write them by using the Azure blob storage API.

In an Azure Storage Account, you store blobs in containers. A container provides a convenient way of grouping related blobs together. You control who can read and write blobs inside a container at the container level.

Within a container, you can organize blobs in a hierarchy of virtual folders, similar to files in a file system on disk. However by default these folders are simply a way of using a "/" character in a blob name to organize the blobs into namespaces. The folders are purely virtual, and you can't perform folder-level operations to control access or perform bulk operations.

https://mystorageaccount.blob.core.windows.net
  • AzureStorageAccount
    • Container1
      • Blob2
      • Folder1/Blob2
    • Container2
      • Folder2/Blob3
      • Folder2/Blob4

Objects in Blob storage are accessible via:

  • Azure Storage REST API
  • Azure Storage Client Library
  • Azure PowerShell
  • Azure CLI

Types of blob data

Azure Blob Storage supports three different types of blob:

  • block
    • they are best used to store discrete, large, binary objects that change infrequently
  • page
    • a page blob is optimized to support random read and write operations
    • a page blob can hold up to 8 TB of data
    • Azure uses page blobs to implement virtual disk storage (VHD) for virtual machines
  • append:
    • an append blob is a block blob optimized to support append operations
    • you can only add blocks to the end of an append blob
    • updating or deleting existing blocks isn't supported
    • the maximum size of an append blob is just over 195 GB

Access tiers for blob data

Blob storage provides three access tiers, which help to balance access latency and storage cost:

  • Hot tier
    • it is the default
    • it is used for blobs that are accessed frequently
  • Cool tier
    • lower performance and reduced storage charges (compare to Hot tier)
    • it is used for blobs that are accessed infrequently
  • Archive tier
    • it provides the lowest storage cost, but with increased latency
    • it is intended for historical data that must not be lost, but is required only rarely
    • blobs in the Archive tier are effectively stored in an offline state

Lifecycle Management Policies

A lifecycle management policy can automatically move a blob from Hot to Cool, and then to the Archive tier, as it ages and is used less frequently (policy is based on the number of days since modification).

A lifecycle management policy can also arrange to delete outdated blobs.