When you make a backup of SQL server using VSS or a third party tool... what happens?
It says it freezes I/O, VSS gets a snapshot then it resumes I/O... but what is going on there?
If I have a 20 TB database to snapshot it is going to take me more than 60 seconds right?
So that entire time does VSS maintain a differential snapshot or something that I backup where each change is recorded by VSS as it differs from the original?
SQL server keeps working and if 50 million rows are deleted then VSS adds a differential to it's snapshot of those 50 million rows so they will be there for my backup to work with?
Am I completely misunderstanding how this all works?