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Published byClementine Woods Modified over 6 years ago
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Modeling and Evaluation of Fibre Channel Storage Area Networks
Xavier Molero, Federico Silla, Vicente Santonia and Jose Duato
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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
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Traditional Server-Storage Architecture
Limitations: Unavailability of data in case of a failure on server Bandwidth saturation during backups
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Typical SAN Architecture
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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)
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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
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System Model Switch Architecture Network Topology Routing Algorithm
Communication Pattern Disk response time model I/O load generation
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Switch Architecture
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Switch Architecture
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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
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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)
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Communication Pattern
Request parameters: Disk ID Access type (read or write) Starting location (sector number) Requested size
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Communication Pattern
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Disk Response Time Model
A single server queue with a FIFO discipline service Composed of three parts: Seek time Rotational latency Transfer time
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Disk Response Time Model
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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
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Evaluating SANs Performance
Effect of switch architectures on performance Effect of faulty links on performance
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Effect of Switch architecture
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Effect of Switch architecture
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Effect of Failures in Links
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Effect of Failures in Links
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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.
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Questions What is a storage area network?
What are the limitations of traditional server-storage architecture? Name some features of fiber channels.
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