because SQL performs disk IO in extents and an extent is 8 pages, each of which are 8KB, for a total of 64KB
Unfortunately that's not true.
http://blog.purestorage.com/what-is-sql-servers-io-block-size/
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability