Introduction To Blob Storage And Its Components

Note - Blobs in Azure storage emulator are limited to 2 GB.

Since Azure is evolving very fast, the above figures are true as of the date the article is published.

Naming and referencing containers and blobs

Blob storage follows RFC standards (RFC 2616, Section 2.2 and RFC 3987) while providing blob to a blob storage. Each resource here will have a unique URI. It becomes easy because every account name is unique and each account contains a container. Two storage accounts can have same container name but there cannot be two containers of the same name in an account. Blobs within a container must have a unique name. URl format for blob storage is as follows.

http://<storage-account-name>.blob.core.windows.net/<container-name>/<blob-name>

Container naming rule

Container must have a valid DNS Name and as per below protocols:

• Name must be in lowercase.
• It must start with a number or letter. Also, it can contain only letters or numbers.
• It can also contain dash [-] but it should be immediately preceded or followed by a letter or number.
• Minimum length for a container is 3 characters and maximum length is up to 63 characters long.

Blob naming rules

Blob name must follow the following rules:

• Blob names are case-sensitive and contain a combination of characters.
• Minimum length range of a blob can be 1 to 1024 characters and the number of path segments can be up to 254 (path segments are delimiters (/) which can be thought of as a virtual directory path).
• Reserved URL characters must be escaped.

Example

Let’s understand the naming rules with an example. Suppose, we are working on a video library project like YouTube. In these types of projects, raw data (video files) are very important. Thus, it is very important to store them in an organized way so that by looking at the URL, we can get some information about the file. Let’s see how we can categorize files in Azure storage.

URL in blob storage contains 3 components as we have discussed above. First component is storage account which, usually, has the name similar to application. So, our URl till now will be.

Suppose, in this application, we will store images and videos (it may contain other assets as well). Then, we need to create 2 containers.

So far, we have categorized our assets on the basis of type of file. We can further categorize our assets by using delimiters in the blob name and form virtual directory path.

Suppose, we want to further categorize our video with movies, songs, series etc. We can easily do that by adding one more delimiter as below.

We can further categorize our movies on language basis (English, Hindi) as below.

At last, we can add our file name to the URL, as shown below.

In this way, we can add up to 254 delimiters but the entire URL length must be less than or equal to 1024. So, as per above rule, our blob name will be /movies/Hindi/Don.mp4 inside container videos under the service account named as YouTube. The URL is very easy to understand and provides basic metadata about the file.

References

• https://docs.microsoft.com/en-us/azure/storage/storage-dotnet-how-to-use-blobs
• https://docs.microsoft.com/en-us/azure/guidance/guidance-naming-conventions
• https://docs.microsoft.com/en-us/rest/api/storageservices/fileservices/blob-service-concepts