Originally posted by jmodic
Hm, I wouldn't say it is irrelevant. It would be (more or less) irrelevant if you had OS block size of 4K and DB_BLOCK_SIZE of 8K, but not the other way arround as the original poster asked.

If you have 8K OS block size and 4K database block size, then for every single block I/O operation the database requests, the OS will read an extra 4K of data the database hasn't asked for.
Jurij :

Ofcourse OS will fetch the extra 4K for single block I/O request, but I intended to say "Irrelevent" with respect to Performance Issue, because OS always fetechs in multilples of it Block Size limited my Max I/O per fetch.

So have DB Block_Size 8K or 4K, you will get 8K blocks per request (considering 8K block size as said by poster).
So, the Q of performance is Irrelevent, coz in any case you will get non requested data as well.

Abhay.