What happens in Offload/Restore
When a SharePoint Document Library item is offloaded to Microsoft Azure Blob Storage, the binary part of each version is created as a separate Blob.
The original binary part of the document library item is replaced by a small file (<1k) containing the storage reference for the blob in Azure Blob Storage in clear text.
To visually show that the entire file or version is offloaded, the existing (if any) Check-In comment is prefixed by*
"SMART Offload: <Timestamp> <File size> while keeping the original comment on the second line of the comment.
Everything else about the Item is untouched including all metadata and version history metadata.
When the file is Restored it is the reverse that happens. The binary parts of the versions are Restored and the prefix in the Check-in comment is removed.
Note that you can opt to offload the entire file including the current version or just the version history while keeping the current version of the file to keep search index and Copilot intact.
When keeping the current version anyone can edit the file and create new versions that can then incrementally be Offloaded.
Security/Connecting to Microsoft Azure Blob Storage
Shared Access Signature (SAS Token) is used as the only means of authentication.
This method provides the highest level of flexibility and security and enables you to set a variety of restrictions including IP address of the machine(s) able to connect.
Blob Storage Access Tier
The default Access Tier is used. And you can use the Lifecycle management to move blobs to another less expensive Tier for example Archive
Link to Microsoft pricing
Blob naming convention
Each blob has a unique name.
The name format: <SharePoint URL> <Version> <GUID (8-4-4-4-12 format)>
Example:
Tenant/sites/Site/Library/Folder/Filename 1.0 xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
Blob Index tags
The purpose of index tags is to be able to search the blob container.
Each file version is tagged with the below listed tags.
Please note that Azure stores all index tags as text. Therefore observe the format.
Important: You cannot use hierarchical namespace since it i greatly limited and does not support the use Index-tags among other key technologies.
| Tag name | Format | Description |
|---|---|---|
| RestoreDate | yyyy-mm-dd hh:mm:ss | The timestamp for when the file version was last restored to a SharePoint Document Library. |
| UploadDate | yyyy-mm-dd hh:mm:ss | The timestamp for when the file version was uploaded to blob storage. |
| SharePointModifiedDate | yyyy-mm-dd hh:mm:ss | The SharePoint column [Modified]. |
| Size | prefixed with 0 up to 12 digits to allow for numeric query | The size in bytes of the file version. |
| GUID | 8-4-4-4-12 standard format | The SharePoint column [Unique Id]. In SharePoint all versions of a file has the same GUID. |