Transcript Modeling and Evaluation of Fibre Channel Storage Area Networks

Modeling and Evaluation of
Fibre Channel Storage
Area Networks
Xavier Molero, Federico Silla,
Vicente Santonia and Jose Duato
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
Traditional ServerStorage Architecture
Limitations:
Unavailability
of data in case
of a failure on
server
Bandwidth
saturation
during backups
Typical SAN
Architecture
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)
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
System Model
Switch Architecture
Network Topology
Routing Algorithm
Communication Pattern
Disk response time model
I/O load generation
Switch Architecture
Switch Architecture
Network Topology
Single room

Regular:
Fattrees, meshes, multistage networks, and fully
connected topologies

Irregular:
randomly generated, a single link connects two
switches
Floor topologies
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)
Communication Pattern
Request parameters:
Disk ID
 Access type (read or write)
 Starting location (sector number)
 Requested size

Communication Pattern
Disk Response Time
Model
A single server queue with a FIFO
discipline service
Composed of three parts:
Seek time
 Rotational latency
 Transfer time

Disk Response Time
Model
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
Evaluating SANs
Performance
Effect of switch architectures on
performance
Effect of faulty links on performance
Effect of Switch
architecture
Effect of Switch
architecture
Effect of Failures in
Links
Effect of Failures in
Links
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.
Questions
What is a storage area network?
What are the limitations of traditional
server-storage architecture?
Name some features of fiber channels.