Pros/Cons of using multiple databases vs using a single database

Question

I was working on a new project which has the requirement to use 7 databases, arguing that performance, stability, optimization are more easily implemented. While I don't agree, I'm having trouble collecting good arguments to use a single database (splitting the tables into logical domains). One argument I have so far is data integrity (I can't use foreign keys between databases). What are good pros/cons for using a single or multiple databases? [summary so far] Arguments against multiple databases: Losing data integrity (can't use foreign keys over databases) Losing restore integrity Gaining complexity (db users/roles) Small odds server/database will go down Solutions: Use schemas to separate domains. POC: Use dummy data to prove the point in 7/1 db's execution plans JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

None of performance, stability, optimization are true. Does anyone have a solid argument or reference article why these would be true? Resources are not allocated to a database: the SQL Server Instance balances resources so it makes no difference You lose: data integrity restore integrity (data in DB7 will be later then DB1) You gain complexity: security (users, roles etc) have to be in all databases you'll have some data that doesn't fit into 1 database nicely Options: splitting a database onto separate disks can be done with filegroups use schemas to logically separate data (based on other answer)