Disk I/O

Hello,

we are using a 9.2.0.5 DB on a Windows Advanced Server machine having 8 * 1.8 GHz CPUs, 8GB of MM.
The database is used as well as DW as also as OLTP system. Data is stored on three Clariion RAID5 / fiber channel disk systems. When monitoring the database I can see lots of disk waits, which is expected when considering the relation CPU performance / number of disks. However, when looking at the Clariion performance monitor, I see between 40 and 80 IO requests / sec and between 0 and 4 queued IO requests. The queue size does not raise during regular DB operation. When doing additional disk operations via OS, as e.g. copying a file, IO requests raise up to 600 / sec.

The question is: Why is the DB waiting for IO, while the disks seem not to work at their limits? Received on Wed Mar 16 2005 - 23:39:30 CST