SQL Server Storage Engine under the hood
Enterprise Database Administration & Deployment
How SQL Server performs I/O
How is SQL Server really accessing the data and log files on the disk? What's done asynchronous and what's synchronous and what impact does that have on our queries and DML statements.
Which impact have features like database mirroring and replication, what's different when SQL Server is starting up.
Which I/O Subsystems (including SSD) are best for which type of data and what's the impact if you choose a different one. Which files can be placed on the same volume and which should not.