2. ICC Module 3 Lesson 3 – Storage 1 / 4 © 2015 Ph. Janson Information, Computing & Communication Storage – Clip 0 – Introduction School of Computer Science & Communications A. Ailamaki, Ph. Janson, W. Zwaenepoel

3. ICC Module 3 Lesson 3 – Storage 2 / 4 © 2015 Ph. Janson Where do we stand ? 1 GHz clock Proc On-chip memory Off-chip memory FLASH Hard disk Magnetic tape 1-10ns, 100MB 100ns, 100GB 10µs, 1TB 1ms, 1TB minutes, 1PB Storage Memory Automatic LRU management Semi-automatic management Speed Size Cache defaults Block size Semi-automatic = automatic transfer after “manual” request Performance Size

4. ICC Module 3 Lesson 3 – Storage 3 / 4 © 2015 Ph. Janson Why do we need storage management ? ►Central memory is  Volatile  Too expensive  Too small ►Storage management is thus necessary  To save all data at reasonable cost over the long term ►Data transfer between storage  memory is semi-automatic  It is governed by the same principle of locality as memory  cache transfers  With the same success in performance thanks to the same LRU algorithm  But it requires steering the system to find desired data as needed  It happens in pages of several KB instead of blocks of a few bytes ►Where and how to store data so they can be retrieved?

5. ICC Module 3 Lesson 3 – Storage 4 / 4 © 2015 Ph. Janson Outline ►Clip 1 – Technology reminder & basic principleClip 1 ►Clip 2 – Storage structuresClip 2 ►Clip 3 – Addressing and namingClip 3 ►Clip 4 – File systemsClip 4 ►Clip 5 – DatabasesClip 5