AK Gonzalez summaries some changes:
For years, database professionals faced a frustrating limitation. With Availability Groups, you could offload some workloads to secondary replicas—but not your real backup strategy.Yes, you could run copy-only backups on a secondary. But true full backups? Differential backups that maintain the LSN chain? Those had to run on the primary replica, until now. SQL Server 2025 introduces the ability to run true full backups and true differential backups on secondary replicas.
Read on to see what this means. AK also looks at the change to ZSTD for backup compression and immutable backups in Azure Storage.
One thing I would want to warn anybody (or any company) looking into using immutable storage for backups is, Microsoft’s not joking about that immutability. That includes deleting them when you see what the bill is going to be. You can set retention polices to delete these automatically, but that’s the only way you’re getting rid of those old backups. And just because they’re old doesn’t mean you get charged less for the privilege of storing them off-site.