What service tag should be allowed in NSGs to facilitate writing data to the cache storage account from the VM?

Allowing the Storage service tag in Network Security Groups (NSGs) is essential for facilitating communication between virtual machines (VMs) and Azure Storage accounts. When VMs need to write data to a cache storage account, they need to access the associated Azure Storage services. The Storage service tag encompasses the necessary IP addresses and endpoints that are required to enable this communication.

By allowing the Storage service tag, you ensure that all relevant storage operations are permitted, which includes writing data and other management tasks associated with Azure Storage. This streamlined access is vital for applications running on the VMs that require interaction with the storage layer.

The Compute service tag typically pertains to resources related to virtual machines themselves and does not include storage operations. The Network service tag is focused on network resources but doesn't provide access to storage services. The Web service tag generally relates to web-related services and is not relevant for direct interactions with storage accounts. Thus, allowing the Storage service tag is the most appropriate configuration to facilitate writing data to cache storage from a virtual machine.