1. Agenda Nestle Case (continued) Data Management Chapter 5 Review Chapter 6 Review

2. Nestle Case Lessons Learned (last week) Discussion: Lack of “buy-in” from functional management: –Causes? –Solutions?

3. Data Storage Character Sets File Systems Storage Arrays and RAID Network File Systems Internet File Systems Storage Area Networks Network Attached Storage

4. Character Sets Representations of all text elements ASCII – Standard for PC’s, unix EBCDIC – Mainframe standard UNICODE – The web standard: many more characters Sorting Implications –ASCII: 1Aa –EBCDIC: aA1

5. Ascii Character Set Example (with even parity) _ _ _ _ 1 1 1 0 0 0 0 1 = a 0 1 0 0 0 0 0 1 = A 0 0 1 1 0 1 0 1 = 5

6. File System Concepts and Issues File Allocation Table Disk Sectors and Fragmentation Hierarchical File Systems Journaled vs raw file systems Disk Caching Mechanism Reason

7. Hierarchical File System win data pgm txt bin src exe

8. Caching Data Disks Process Cache memory Read-ahead Write to disk

9. Shared Storage Arrays Vendors: StorTek, IBM, EMC, HP, … Goals: Management, flexibility Issues: Connectivity Virtual Storage

10. RAID (redundant array of independent disks) RAID 0 (Striping) –Consecutive blocks written to different disks –Performance gain only RAID 1 (Mirroring) –Writes all data to two separate drives –Reads from either for performance RAID 5 (Parity disk) –Any disk can fail without loss –Parity drive allows failed drive to be recreated

11. RAID 0 Diagram (Striping) Disk A Disk B Disk C Disk D Block 1 Block 2 Block 3 Block 4

12. RAID 1 Diagram (Mirroring) Disk A Disk B Block 1

13. RAID 5 Diagram (with even Parity) Disk A Disk B Disk C Disk D Parity Disk 1 0 0 1 0 0 1 1 1 1 0 0 0 1 1 1 1 1 0 1 block1 block2 block3 block4 paritydata

14. Remote Data Network File Systems Internet File Systems Considerations: Performance Security “Roaming”

15. Storage Area Networks “Fabric” connectivity between servers and storage Access is still via “owning” server Used for structured data, data associated with specific application

16. “Fabric” Storage Area Network Server 1Server 2Server 3Server 4 SAN Side 1 SAN Side 2 Disk A Disk B Disk C Disk D Disk E

17. Network-Attached Storage File systems accessed via internet Appear as remote drives Used for unstructured data (e.g. documents), data used by many servers

18. NAS Diagram Network Server NAS

19. Discussion What might determine whether we will use SAN or NAS in a network design?

20. Chapter 5 Review Data availability, not processing power, is the limiting factor Distributing functions vs distributing control: Scope –Does distributed computing imply distributed control? Security and access implications

21. Chapter 6 Review Digital Convergence –Satisfice vs excellence Mead’s law: the logic behind the internet Messaging: The next killer app