Slow download speed from Azure Storage

Question

While testing our storage virtualization solution for a client we found interesting situation:

1. When object is downloaded directly from Azure Blob Storage to outside of Azure - the speed (tested by wget) is around 0.2 to 0.5 MB/s
2. When the same object is downloaded to a VM in Azure - the speed is around 60 MB/s

It may seem like a network issue, but....

3. When the same object is downloaded via our proxy that also runs in the same Azure region and actually downloads the same object from Azure Blob Storage without any caching (and converts to S3 which is irrelevant here) - the speed is 30 MB/s and is basically limited by client's network.

I tried different regions and the results are similar.

Is Azure somehow throttles traffic coming from Blob storage to outside of Azure?

Answer 1

Your proxies/VMs or whatever runs in the same datacenter, network requests does not leave the local network and the speed then depends on the infrastructure. (routers, firewalls, cables, etc ...). I'm sure they won't limit speed between their own infrastructure so services hosted on the same network works at full speed.

When you download from outside the datacenter, it depends on the outside architecture. And then your speed depends on more factors, including your internet downloading speed. Maybe they also limit uploading speed on their side but 0.5 MB would be very low.

EDIT: even between different region, you will benefit of 2 VMs connected through optic backbones. That's normal to have a high speed. They can also consider the traffic is "inside" Azure even if it's not the same datacenter and so not limit downloading speed.

Did you tried to download from a fast internet connection outside of the datacenter ? For exemple setting up a VM on digitalocean and trying a wget from this machine ?