November 5, 2005 at 7:39 am
It is said that the data page is the smallest unit of I/O for SQL Server. But at the operating system level, the smallest unit of I/O is the OS block, not a data page which consists of several OS blocks. Does it mean that SQL Server requests the OS to read all the OS blocks comprising a data page together and then pass them on to SQL Server so that SQL Server can process the complete data page as one whole.
November 7, 2005 at 12:51 am
As I mentioned in an earlier answer to one of your questions, the smallest unit of I/O that SQL Server reads from disk are extents. An extent contains 8 pages, so it is 64K. And yes, it means that SQL Server requests the OS to read all of the 64K and then treat that as an entire extent.
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