Agenda

• Data Storage

• Database Management Systems

• Chapter 3

• AOL Time-Warner Case

Data Storage

• Character Sets

• File Systems

• RAID File Storage

• Network File Systems

• Internet File Systems

• Storage Area Networks

• Network Attached Storage

Character Sets

Representations of all text elements

ASCII – Standard for PC’s, unix

EBCDIC – The Mainframe alternative

UNICODE – The web standard

File System Concepts and Issues

File Allocation Table (FAT) / Volume Table of Contents (VTOC)

Disk Sectors and FragmentationHierarchical File SystemsJournaled vs raw file systemsDisk Caching

MechanismReason

Shared Storage Arrays

Vendors: StorTek, IBM, EMC, …

Goals: Management, flexibility

Issues: Connectivity

Virtual Storage

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

RAID 0 Diagram(Striping)

Disk A

Disk B

Disk C

Disk D

Block1

Block2

Block3

Block4

RAID 1 Diagram(Mirroring)

Disk A

DiskB

Block1

RAID 5 Diagram(Even Parity)

Disk A

Storage Mechanism

Disk B

Disk C

Disk D

ParityDisk

1 0 0 1 0

Remote Data

Network File Systems

Internet File Systems

Considerations:Performance

Security

“Roaming”

Storage Area Networks

“Fabric” connectivity between servers and storage

Access is still via “owning” server

Used for structured data, data associated with specific application

“Fabric” Storage Area Network

Server 1 Server 2 Server 3 Server 4

SAN Side 1 SAN Side 2

DiskA

DiskB

DiskC

Disk D

DiskE

Network-Attached Storage

File systems accessed via internet

Appear as remote drives

Used for unstructured data (e.g. documents), data used by many servers

NAS Diagram

Network

Server Server

NAS

Database Management Systems

• Programs that manage databases• Link different data structures logically• Single version of all rules

– Structures– Domains– Access

• Data reliability enhancements– Locking– Logging– Journaling

• Standard “API”– SQL: Structured Query Language

• Granular Access

Relational DBMS Concepts

• Value-based relations

• Joins

• Tables and Views

• Set Processing

Text Chapter 3: Themes

• Networking the Business – “Act big and small”– “Fast firms”

• Blueprint– Operating Processes – Managing and learning

• Value Networks– Virtual Integration– Cost/Risk Analysis– Market Relationships– Proprietary processes vs Virtual Integration

Text Chapter 3: Discussion

• What systems enable “company-smart” decisions

• When does “scope of control” effect growing firms

Case: AOL Time Warner

• Is the company successful?

• Explain stock drop vs other Internet “servicers”

• What (if any) “rules” were broken?