Question

Suppose I create a Windows Azure application that consists of multiple instances talking to each other by starting a server on each instance and exchanging big chunks of data.

What data transfer speed should I expect from the underlying infrastructure?

Answer 1

It depends a bit on what size your instances are:

• XS instance: 5 Mbps max
• S: 100 Mbps sustained, ~250 Mbps bursts
• M: 200 Mbps sustained, ~ 4-500 Mbps bursts
• L: 400 Mbps sustained, upto 800 Mbps bursts
• XL: 800 Mbps – you get whole NIC

Those are the limits. There are other factors as well of course:

1. Are you communicating within a datacenter (sub-region)? Assuming yes here.
2. Are you using affinity groups? That would put you in same stamp and you could minimize switch traffic – not a huge deal typically as NIC is slowest, but it would help latency a tiny bit. If this is all within a role, you are definitely in same affinity group and same deployment.
3. Are you writing to disk to buffer communication? Disk IO speeds are different between instances as well. If you are buffering large files or something to disk, you will see overall IO drop as the disk tries to keep up. XL instances have best IO performance.

There are likely other factors as well, but these are what I can think of off the top of my head.