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iSCSI Performance Experiments

iSCSI Performance Experiments. Li Yin EECS Department U.C.Berkeley. Outline. Introduction iSCSI iSCSI Performance Challenges Experimental Plan. Network Attached Storage. Storage Area Networks. Introduction. Networked Shared Storage In contrast to direct attached storage

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iSCSI Performance Experiments

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  1. iSCSI Performance Experiments Li Yin EECS Department U.C.Berkeley

  2. Outline • Introduction • iSCSI • iSCSI Performance Challenges • Experimental Plan

  3. Network Attached Storage Storage Area Networks Introduction • Networked Shared Storage • In contrast to direct attached storage • High availability • Better resource sharing • Easy to manage • NAS vs. SAN

  4. IP SAN • Transport SCSI over IP Networks • Less cost • Longer operating distance • Leverage existing technology and management tools • Protocols to transport SCSI over IP Networks • FCIP , iFCP ,iSCSI

  5. iSCSI • Encapsulates SCSI command in TCP packets • SCSI commands are encapsulated into iSCSI protocol data unit (PDU). • PDUs are sent over one or more TCP connections. • TCP as the transport protocol • Provides the reliability and congestion control method • The most dominant transport protocol • Well-supported

  6. iSCSI Performance Challenges • TCP processing overhead • Security • Packet drops • Delay caused by long distance • …

  7. Experiments Setup • Testbed: • Initiator: • Intel initiator • Router: • Current: NistNet controls delay, bandwidth and drop rate • Future: Router VM • Target: • DiskSim as the iSCSI target

  8. Experimental Plan • Performance Metrics: • Throughput • I/O Rate • Three steps: • iSCSI on a separated LAN • iSCSI on a LAN with cross traffic • iSCSI on a WAN

  9. Preliminary result • To test the impact of packet drop, delay and request size on the overall throughput. • Setup: • Ignore the disk mechanical impact • Delay = 10ms • Bandwidth = 100Mb/s • NistNet to generate random drop • Continuously write/read (100 times) equal size request to/from the target

  10. Delay vs Throughput (ms)

  11. Drop Rate vs. Throughput

  12. Experimental Plan (Cont.) • Issues to focus on: • How to maintain a high performance with packet drops? • Performance drop due to • Bandwidth shrink • Head of Queue blocking • Bandwidth provision? • Might be expensive. • Router queue management mechanism with the assistance of PNE? • Multiple TCP Connections? • Higher overall bandwidth. • Smart scheduling?

  13. Experimental Plan (cont.) • How to achieve high performance with a long delay? • Proxy? • Cache /Pre-fetching? • Initiator buffer? • Avoid retransmission?

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