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Kulveer Singh Graduate School of Design & IT Dongseo University

Data Concurrency Issues in iSCSI Based-Data Storages. Kulveer Singh Graduate School of Design & IT Dongseo University Busan, South Korea. Outline. Introduction Concurrency Issues

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Kulveer Singh Graduate School of Design & IT Dongseo University

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  1. Data Concurrency Issues in iSCSI Based-Data Storages Kulveer Singh Graduate School of Design & IT Dongseo University Busan, South Korea KIMICS 2006

  2. Outline Introduction Concurrency Issues Hierarchical Locking System Design & Simulation Simulation Results Conclusion References KIMICS 2006

  3. 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 KIMICS 2006

  4. iSCSI stack Initiator : System which request block level data from Target Target : System which receive the SCSI commands from Initiator KIMICS 2006

  5. Main Reason For Concurrency • No Centralized Locking mechanism implemented. • No Cache consistency semantics used at the initiators. KIMICS 2006

  6. Concurrency Issue KIMICS 2006

  7. Design Approach KIMICS 2006

  8. Hierarchical Locking System Compatibility Table • * Indicates conflict • S Share lock • X Exclusive lock • IS Intention Share • IX Intention exclusive KIMICS 2006

  9. Central Metadata Manager (CMM) • Lock Table consists of • Block ID • Conflict Count • Group Mode • Lock Queue • Wait Queue KIMICS 2006

  10. Ns2 (Network Simulator) • Applications in Ns2 are virtual • Does not transfer data. • Packets are generated at transport layer by transport agent. • Send at particular intervals according to the application specification. KIMICS 2006

  11. Simulation Model in Ns2 iSCSI Application Class iscsiInitApp Agent iscsiRouterApp Agent iscsiTargetApp Agent KIMICS 2006

  12. iSCSI layer implementation In Ns2 • iSCSI layer on top of Full TCP agent • iSCSI layer will be able to send data according to the user requirement. • iSCSI layer composed of user interface layer and iSCSI agent. User Interface iSCSI agent iSCSI layer KIMICS 2006

  13. Layer architectureIn NS iSCSI layer Send_data (PDU) Process_data (PDU) Agent Wrapper (Full TCP agent) Send (bytes) Recv. (bytes) TCP base class Packets KIMICS 2006

  14. 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. KIMICS 2006

  15. SimulationParameters • 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. KIMICS 2006

  16. Result of Varying Read/Write Access Pattern for LAN • The parameters are • Number of LUN = 4 • Allotted Time = 10 • Directory Depth = 2 KIMICS 2006

  17. Result of Varying Number of Initiators Sharing a LUN for LAN • The parameters are • Read: Write Ratio = 60:40 • Allotted Time =10 • Directory Depth = 2 KIMICS 2006

  18. 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. KIMICS 2006

  19. 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/ KIMICS 2006

  20. Questions? KIMICS 2006

  21. Thank You kulveer@dongseo.ac.kr KIMICS 2006

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