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Data Concurrency Issues in iSCSI Based-Data Storages. Kulveer Singh Graduate School of Design & IT Dongseo University Busan, South Korea. Outline. Introduction Concurrency Issues - PowerPoint PPT PresentationTRANSCRIPT
July 14, 2006 1KIMICS 2006
Kulveer Singh Graduate School of Design & IT
Dongseo University Busan, South Korea
Data Concurrency Issues in iSCSI Based-Data Storages
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Outline
Introduction
Concurrency Issues
Hierarchical Locking System
Design & Simulation
Simulation Results
Conclusion
References
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iSCSI Defined: What Is iSCSI? iSCSI = internet Small Computer System Interface An interconnect protocol that:
Is designed for storage area networks (SANs) Supports the block-based storage needs of database applications Is TCP/IP based Establishes and manages connections between IP-based storage devices, hosts
and clients Is based on familiar and ubiquitous open standards Provides advanced IP routing, management, and security tools
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iSCSI stack
Initiator : System which request block level data from TargetTarget : System which receive the SCSI
commands from Initiator
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Main Reason For Concurrency
No Centralized Locking mechanism implemented.No Cache consistency semantics used at the initiators.
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Concurrency Issue
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Design Approach
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Hierarchical Locking System
* Indicates conflict• S Share lock• X Exclusive lock• IS Intention Share• IX Intention exclusive
S X IS IX
S * *
X * * * *
IS *
IX * *
Compatibility Table
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Central Metadata Manager (CMM)
Lock Table consists of Block ID Conflict Count Group Mode Lock Queue Wait Queue
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Ns2 (Network Simulator)
Applications in Ns2 are virtualDoes not transfer data.Packets are generated at transport layer by transport agent.Send at particular intervals according to the application specification.
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Simulation Model in Ns2
iscsiInitApp Agent iscsiRouterApp Agent iscsiTargetApp Agent
Application Class
iSCSI
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iSCSI layer implementation In Ns2
iSCSI layer on top of Full TCP agentiSCSI layer will be able to send data according to the user requirement.iSCSI layer composed of user interface layer and iSCSI agent.
iSCSI agent
User Interface
iSCSI layer
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Layer architecture In NS
iSCSI layer
Agent Wrapper(Full TCP agent)
TCP base class
Process_data(PDU)
Send_data (PDU)
Recv. (bytes)Send (bytes)
Packets
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Initiator & Target Simulation
Initiator will use the same layer architecture defined above.Target (iSCSI router) will also use the same architecture except the user interface layer will be eliminated from iSCSI layer.
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Simulation Parameters
Read/Write Access Pattern.Number of initiators sharing a LUN (Logical Unit Number).Allotted Time for the Exclusive Locks.Directory Depth.
Throughput Measured as the average number of locks granted
per initiator per minute by the CMM.
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Result of Varying Read/Write Access Pattern for LAN
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
Thro
ughp
ut/m
in
30 40 50 60 65 70 75 80 85 90Read Percentage
Effect of Read/Write Ratio on Avg. Throughput
Write Throughput Throughput Read Throughput
The parameters are Number of LUN = 4 Allotted Time = 10 Directory Depth = 2
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Result of Varying Number of Initiators Sharing a LUN for LAN
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
180.0
200.0
2 3 4 5 6 7 8# of Initiators
Effect of # of Initiators on Avg. Throughput
Write Throughput Throughput Read Throughput
The parameters are Read: Write Ratio = 60:40 Allotted Time =10 Directory Depth = 2
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Conclusion
Design has been validated by the NS2 simulator and the study of various parameters has been done.
Now the design can be practically implemented on the iSCSI router and performance can be measured practically.
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References
[1] Simulation of Hierarchical Locking Scheme for ISCSI SAN File Sharing – A Plan B report by Fang Zhang
[2] Caching in the Sprite Network File System - Michael N. Nelson, et al.[3] Metadata Update Performance in File Systems - Gregory R. Ganger and Yale N. Patt[4] Scalable Session Locking for a Distributed File System - Randal C. Burns, et al.[5] An Overview of the Global File System - He and Qing Yang.[6] The Linux Virtual File-system Layer - Neil Brown, et al.[7] The Network Simulator - Ns-2 http://www.isi.edu/nsnam/ns/[8] Ns by example – Jae Chung and Mark Claypool http://nile.wpi.edu/NS/
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Questions?