I am investigating migrating an on-premises SQL Server availability group to an Azure SQL Managed Instance (2 databases, 600 tables, 3TB, of which 2TB is blobs).
A significant amount of on-premises reporting occurs that would be costly to change, and pulls large portions of the database on a nightly basis.
I would like to be able to add an on-premises read-only secondary to the Managed Instance's availability group. This would prevent existing reporting from flooding our ExpressRoute and costing a lot of money in data transfer.
I know Azure Data Sync (preview) exists, but the simplicity of just-another-secondary allures me. I know I could do this manually with IaaS options, but am looking to avoid the operational overheads. Does anyone have good news for me?
I took this question to my local Microsoft cloud architects, and they agree that an on-prem replica of a Managed Instance availability group isn't possible at the moment. The docs explicitly state that a Managed Instance can't be the publisher in a transactional replication setup either. For now our design will do reporting over the ExpressRoute.
It's worth noting that the MS chaps thought I was overly concerned about moving data over the ExpressRoute, citing larger clients that move around 5TB / week, every week, without a problem (we can get a 10Gbps ExpressRoute if need be).