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Set or change a block blob's access tier with .NET

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This article shows how to set or change the access tier for a block blob using the Azure Storage client library for .NET.

Prerequisites

Set up your environment

If you don't have an existing project, this section shows you how to set up a project to work with the Azure Blob Storage client library for .NET. The steps include package installation, adding using directives, and creating an authorized client object. For details, see Get started with Azure Blob Storage and .NET.

Install packages

From your project directory, install packages for the Azure Blob Storage and Azure Identity client libraries using the dotnet add package command. The Azure.Identity package is needed for passwordless connections to Azure services.

dotnet add package Azure.Storage.Blobs
dotnet add package Azure.Identity

Add using directives

Add these using directives to the top of your code file:

using Azure.Identity;
using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;
using Azure.Storage.Blobs.Specialized;

Some code examples in this article might require additional using directives.

Create a client object

To connect an app to Blob Storage, create an instance of BlobServiceClient. The following example shows how to create a client object using DefaultAzureCredential for authorization:

public BlobServiceClient GetBlobServiceClient(string accountName)
{
    BlobServiceClient client = new(
        new Uri($"https://{accountName}.blob.core.windows.net"),
        new DefaultAzureCredential());

    return client;
}

You can also register a service client for dependency injection in a .NET app. To learn more about creating and managing client objects, see Create and manage client objects that interact with data resources.

Authorization

The authorization mechanism must have the necessary permissions to set a blob's access tier. For authorization with Microsoft Entra ID (recommended), you need Azure RBAC built-in role Storage Blob Data Contributor or higher. To learn more, see the authorization guidance for Set Blob Tier.

About block blob access tiers

To manage costs for storage needs, it can be helpful to organize your data based on how frequently it's accessed and how long it needs to be retained. Azure storage offers different access tiers so that you can store your blob data in the most cost-effective manner based on how it's being used.

Access tiers for blob data

Azure Storage access tiers include:

  • Hot tier - An online tier optimized for storing data that is accessed or modified frequently. The hot tier has the highest storage costs, but the lowest access costs.
  • Cool tier - An online tier optimized for storing data that is infrequently accessed or modified. Data in the cool tier should be stored for a minimum of 30 days. The cool tier has lower storage costs and higher access costs compared to the hot tier.
  • Cold tier - An online tier optimized for storing data that is infrequently accessed or modified. Data in the cold tier should be stored for a minimum of 90 days. The cold tier has lower storage costs and higher access costs compared to the cool tier.
  • Archive tier - An offline tier optimized for storing data that is rarely accessed, and that has flexible latency requirements, on the order of hours. Data in the archive tier should be stored for a minimum of 180 days.

To learn more about access tiers, see Access tiers for blob data.

While a blob is in the Archive access tier, it's considered to be offline, and can't be read or modified. In order to read or modify data in an archived blob, you must first rehydrate the blob to an online tier. To learn more about rehydrating a blob from the Archive tier to an online tier, see Blob rehydration from the Archive tier.

Restrictions

Setting the access tier is only allowed on block blobs. To learn more about restrictions on setting a block blob's access tier, see Set Blob Tier (REST API).

Note

To set the access tier to Cold using .NET, you must use a minimum client library version of 12.15.0.

Set a blob's access tier during upload

You can set a blob's access tier on upload by using the BlobUploadOptions class. The following code example shows how to set the access tier when uploading a blob:

public static async Task UploadWithAccessTierAsync(
    BlobContainerClient containerClient,
    string localFilePath)
{
    string fileName = Path.GetFileName(localFilePath);
    BlockBlobClient blockBlobClient = containerClient.GetBlockBlobClient(fileName);

    var uploadOptions = new BlobUploadOptions()
    {
        AccessTier = AccessTier.Cool
    };

    FileStream fileStream = File.OpenRead(localFilePath);
    await blockBlobClient.UploadAsync(fileStream, uploadOptions);
    fileStream.Close();
}

To learn more about uploading a blob with .NET, see Upload a blob with .NET.

Change the access tier for an existing block blob

You can change the access tier of an existing block blob by using one of the following functions:

The following code example shows how to change the access tier for an existing blob to Cool:

public static async Task ChangeBlobAccessTierAsync(
    BlobClient blobClient)
{
    // Change the access tier of the blob to cool
    await blobClient.SetAccessTierAsync(AccessTier.Cool);
}

If you are rehydrating an archived blob, you can optionally set the rehydratePriority parameter to High or Standard.

Copy a blob to a different access tier

You can change the access tier of an existing block blob by specifying an access tier as part of a copy operation. To change the access tier during a copy operation, use the BlobCopyFromUriOptions class and specify the AccessTier property. If you're rehydrating a blob from the archive tier using a copy operation, you can optionally set the RehydratePriority property to High or Standard.

The following code example shows how to rehydrate an archived blob to the Hot tier using a copy operation:

public static async Task RehydrateBlobUsingCopyAsync(
    BlobClient sourceArchiveBlob,
    BlobClient destinationRehydratedBlob)
{
    // Note: the destination blob must have a different name than the archived source blob

    // Configure copy options to specify hot tier and standard priority
    BlobCopyFromUriOptions copyOptions = new()
    {
        AccessTier = AccessTier.Hot,
        RehydratePriority = RehydratePriority.Standard
    };

    // Copy source blob from archive tier to destination blob in hot tier
    CopyFromUriOperation copyOperation = await destinationRehydratedBlob
        .StartCopyFromUriAsync(sourceArchiveBlob.Uri, copyOptions);
    await copyOperation.WaitForCompletionAsync();
}

To learn more about copying a blob with .NET, see Copy a blob with .NET.

Resources

To learn more about setting access tiers using the Azure Blob Storage client library for .NET, see the following resources.

REST API operations

The Azure SDK for .NET contains libraries that build on top of the Azure REST API, allowing you to interact with REST API operations through familiar .NET paradigms. The client library methods for setting access tiers use the following REST API operation:

Client library resources

Code samples

See also