Why does the fill factor in SQL Server default to 0 (100%)?

I understand fill-factor, pages and index structure and I therefor understand why a 100% fill factor is a rare best practice. So why does it default to 0 (or 100% ) by default? Why not 90 or 95?

Is there something I'm missing?

Just throwing out a few suggestions here as to why Microsoft would do this:

• They have geared their default to be best possible OLAP performance (less page reads with a fill factor of 0/100)

• They are assuming that INSERTed data will most likely be at the end of the table, making the extra space per page useless

• They are assuming that typically UPDATEd data will not lengthen row data very often, causing a page split

This is just guessing here. The only people that can really answer that question accurately is the SQL Server team themselves.

StackExchange Database Administrators Q#15760, answer score: 8