1. Modeling and Evaluation of Fibre Channel Storage Area Networks
Xavier Molero, Federico Silla, Vicente Santonia and Jose Duato

2. Introduction What is a SAN (Storage Area Network)
A separate high-speed network for storage
Isolated from messaging network
Optimized for moving data between servers and storage devices
How it is different from traditional server-storage network

3. Traditional Server-Storage Architecture
Limitations:
Unavailability of data in case of a failure on server
Bandwidth saturation during backups

4. Typical SAN Architecture

5. Fibre Channel Generic transport mechanism
Provides an interface for high-speed data transfer(gigabit per second) and long distance(up to 10 km)
Standard provides definitions about physical layer characteristics, transport control protocol, and upper level interface to TCP/IP, SCSI, and other protocols
Some features are not specified(routing algorithm, internal switch architecture)

6. Fibre Channel (cont.) Switching Mechanism
virtual cut-through: incoming messages are forwarded as soon as they are routed and out port is free
Flow Control Mechanism
credit scheme

7. System Model Switch Architecture Network Topology Routing Algorithm
Communication Pattern
Disk response time model
I/O load generation

8. Switch Architecture

9. Switch Architecture

10. Network Topology Single room Floor topologies Regular: Irregular:
Fattrees, meshes, multistage networks, and fully connected topologies
Irregular:
randomly generated, a single link connects two switches
Floor topologies

11. Routing Algorithm Distributed routing
Leaving routing decisions to each switch
Up*/down* routing (partially adaptive)
Based on breadth-first spanning tree(BFS)
Minimal adaptive routing (fully adaptive)

12. Communication Pattern
Request parameters:
Disk ID
Access type (read or write)
Starting location (sector number)
Requested size

13. Communication Pattern

14. Disk Response Time Model
A single server queue with a FIFO discipline service
Composed of three parts:
Seek time
Rotational latency
Transfer time

15. Disk Response Time Model

16. I/O Load Generation Use auto-similar arrival pattern
Real traffic is bursty and the bursts exist over many time scales
Model each server as a set of ON/OFF sources
Model the length of ON/OFF periods with Pareto distribution
Simulator can be feed with real-world I/O traces

17. Evaluating SANs Performance
Effect of switch architectures on performance
Effect of faulty links on performance

18. Effect of Switch architecture

19. Effect of Switch architecture

20. Effect of Failures in Links

21. Effect of Failures in Links

22. Summary SAN is a alternative to traditional server-to-disk approach
Fibre channel is a prominent technology for implementing SAN.
The simulator considers a wide set of characteristics and is a key tool for the design and evaluation of SANs.

23. Questions What is a storage area network?
What are the limitations of traditional server-storage architecture?
Name some features of fiber channels.