Azure Premium storage is a relatively new Azure feature that lets you replace your standard storage account with high performance, lower latency storage at an additional cost. Throughput of up to 200MB/s can be achieved with a single disk, and even more if multiple disks are combined on a single server.

This all sounds great, but users of Premium Storage may find themselves disappointed when first testing this hardware, and receive less than advertised performance. What is not made entirely clear in the documentation is that the amount of bandwidth to the storage is restricted based on the VM size in use.

A single P30 disk should provide throughput of around 200MB/s; however, if you attach this to a DS1 virtual machine, you won't see anywhere near this, as the VM is limited to throughput of 32MB/s. To get the advertised 200MB/s throughput, you would need to make use of a DS4 VM which supports up to 256MB/s.

The maximum throughput supported on the DS series is 512MB/s, on a DS14. After that, you will need to look at the GS series which goes up to 5000MB/s but at a hefty price.

The full bandwidth list is below:

DS Series

GS Series