I'm trying to transfer large databases from my on-premises setup to Azure, but it's been a struggle with slow speeds causing frequent failures. I've got a 5Gb express route and recently upgraded to an ultra gateway per Microsoft's advice, but it's not helping. We're only using a fraction of our capacity, and a Microsoft tech confirmed there are no issues on the SQL Server side. The transfer starts at a decent speed of 100MBps but quickly drops down to around 20MBps. It feels like something might be throttling the connection, but I'm at a loss for identifying the problem. Any insights or troubleshooting tips would be appreciated!
5 Answers
You might also want to check the network setup on your on-prem side. What’s the speed of the NIC on your SQL box? Make sure everything—from the switch to the router—can handle the speeds you're aiming for. A bottleneck could exist anywhere in that chain.
Just having a fast connection doesn't guarantee your application can utilize it fully. To check the throughput, try using iPerf, with the client on your premises and the server in Azure. It might help you see if you're maxing out the bandwidth. Also, consider the protocol you're using to transfer the data; that could be where the slowdown is coming from.
Yeah, and if you're using something like SMB over WAN, that could definitely slow things down. It's better to send your databases to blob storage instead.
I noticed you mentioned limited details about your databases. How big are they? Are you dropping backups to blob storage or a VM? The size of your VM can affect transfer speeds too. If you're moving a 100TiB database over a 5GiB connection, expect it to take a long time, so maybe you're just dealing with the inherent time it takes to transfer that much data.
Exactly! And are you doing a live migration with Azure Migrate? That can also introduce different variables.
Also, run some basic troubleshooting on packet loss and latency. This can help identify if the issue lies in the network path from your datacenter to Azure. Sometimes, just simple buffering issues can cause big slowdowns.
Have you looked at the I/O performance on your Azure SQL Server VM? It could be worth backing up to blob storage and using transaction log shipping instead, so you’re not trying to move everything at once which can lead to issues.
For sure! Check internal network speeds too, especially if there's other traffic during your transfers.