I am working with a very large reporting Database (3-4TB) that has nightly ETLs running. We also have a high percentage of fragmentation. I want to defrag the database, but due to the size of the database and the time it will probably take I will need to do this online and may not necessarily be able to run outside of business hours. Which method would least affect end users, backups, and ETLs? Should I just Reorganize, or can I Rebuild with Online parameter?