We recommend that you create a snapshot backup of fewer than 35 databases at the same time.īackup apps like Azure Site Recovery and Veeam don’t warn you about that, though. This can take some time, and while databases are frozen, you’ll see blocking chains for writing queries (which can in turn block readers, too, depending on your isolation level.)īecause of that one-at-a-time problem, KB #943471 says: SQL Server freezes databases one at a time, serially, until it’s got them all frozen. It sounds like witchcraft, but it really does work, and it’s worked for years. These snapshot backups show up in system tables like because when used successfully, they’re like full backups. SQL Server begins writing again, one database at a time (called thawing).VSS tells SQL Server, “You can get back to work”.VSS creates a shadow copy of the data & log files.SQL Server stops writing to each of its databases, freezing them.The VSS service tells SQL Server to freeze its writes.To pull it off, they use the Windows Volume Shadow Copy Service to do snapshot backups – often referred to as VSS snaps. They let you quickly replicate a virtual machine to somewhere else without knowing too much about the server’s contents. Snapshot backup tools like Azure Site Recovery and Veeam are great for sysadmins.
