Understanding SQL Server IO Size

This blog post shows you how NTFS stores data, what the NTFS Allocation Unit means, and how SQL Server performs IOs of variable size. How NTFS Stores Data on Disk A Master File Table (MFT) is the data structure that describes files and directories on NTFS. In Figure 1, you can see an MTF record has several sections describing the metadata about the file and pointers to blocks that make up the file.