SQL Server misunderstanding: 30 days talk about multiple images and log transmission latency of one instance on 7th days

Misunderstanding #7: A database may have multiple images

Error

This misunderstanding is quite common. Each primary server only supports one backup storage. If you want to have copies of multiple master servers, use transaction log transmission. Transaction Log transmission allows multiple secondary instances for each master.

One advantage of using transaction log transfer is that one or more secondary servers can have delayed backup recovery. This means to back up logs on the main server (whether you like it or not, these high availability technologies have their own terms ):

Database image: master server-Backup Server
Transaction Log transfer: primary server-secondary server
Copy: Publishing Server-subscription Server

When using an image, when you drop a table on the master server, the table is also dropped on the backup server (you cannot cancel this operation even if there is a delay ). However, if it is an 8-hour delayed transaction log transfer method, drop the table on the primary server, then the secondary server can still access the table until the log takes effect 8 hours later.

By the way, sqlcat team wrote an articleArticleFor an instance, you can only mirror up to 10 databases. The article is as follows: grouping A large number of databases in a single SQL server instance and another article I wrote about this topic: KB 2001270 things to consider when setting up database processing ing in SQL Server.