DASD Basics

•  I/O is Sloooow
  – Even a cache hit is Ms. vs Mcs. for a pool hit
  I/O costs CPU cycles
  Therefore, all I/O is BAD!!
• Eliminate I/O and you will
  – Run faster
  – Save CPU cycles ($$)

It has been stated for decades that the “only good I/O is NO I/O”.
Therefore, I/O is bad, and even a cache hit in the control unit costs CPU cycles and is orders of magnitude slower than finding the required page in a buffer pool.