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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
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Modeling and Evaluation of Fibre Channel Storage AreaNetworks 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 Server-Storage Architecture Limitations: • Unavailability of data in case of a failure on server • Bandwidth saturation during backups
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
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
Disk Response Time Model • A single server queue with a FIFO discipline service • Composed of three parts: • Seek time • Rotational latency • Transfer time
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
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.