Ingress / Egress data transfer with attached blob drive

Question

Hi,

I was wondering what type of charges we would be hit with if we were to attach a large blob storage volume (e.g. 1TB) to a virtual machine on Windows Azure instead of using a 1TB volume of standard virtual storage attached to the vm as a local disk. Is the pricing fairly similar if we were to use it as cloud backup storage? What type of limitations would we encounter?

I would assume that if data was hitting your vm, then from your vm being sent to Azure Blob storage, that would count as egress transfer from your vm? Or is Azure smart enough to route the traffic internally on the private network instead of over the WAN?

Please share your experience.

Answer 1

As long as the data does not go out of data center, it is not billable. Thus in your scenario if the storage account holding your disk and your vm are in the same data center, you will not be charged for data egress.

Answer 2

Gaurav is (always) right.

Note that when accessing Windows Azure storage, you're charged for transactions ($0.01 for every 100,000 transactions). When you attach a drive backed by blob storage, it's a bit hard to predict how many transactions will be done, because it relates to the OS buffering writes, reads being cached, etc. It's typically not a major component of your bill, but it's something to be aware of, since you asked generally about pricing when you do this.