SQL Server’s I/O Characteristics
A very interesting array from session DAT 334 @ TechEd 2006...
It summarizes the typical IOs issued by SQL Server 2005.
Operation |
Random / Sequential |
Read / Write |
Size Range |
OLTP – Log |
Sequential |
Write |
Sector Aligned Up to 60K |
OLTP – Log |
Sequential |
Read |
Sector Aligned Up to 120K |
OLTP – Data (Index Seeks) |
Random |
Read |
8K |
OLTP - Lazy Writer |
Random |
Write |
Any multiple of 8K up to 256K |
OLTP - Checkpoint |
Random |
Write |
Any multiple of 8K up to 256K |
Read Ahead (DSS, Index/Table Scans) |
Sequential |
Read |
Any multiple of 8KB up to 256K |
Bulk Insert |
Sequential |
Write |
Any multiple of 8K up to 128K |