What is ISER?

Version 11

    This post is intent for InfiniBand/RDMA/ISER newbies that wishes to understand what is ISER, and what are the advantages to use it.

     

     

    References


    What is ISER?

    iSER stands for "iSCSI Extensions for RDMA".  It is an extension of the data transfer model of iSCSI, a storage networking standard for TCP/IP. It uses the iSCSI components while taking the advantage of the RDMA protocol suite.

     

    ISER is an RDMA transport for iSCSI, the link protocol could be either Ethernet or InfiniBand at any supported speed (10,40,56,100Gb/s).

     

    What are the ISER advantages?

    • iSER uses the RDMA protocol suite to supply higher bandwidth for block storage transfers (zero time copy behavior). To that fact, it eliminates the TCP/IP processing overhead while preserving the compatibility with iSCSI protocol.
    • In addition, it has the lowest latency and lowest CPU utilization. Moreover, it enjoys the stability and benefits of the iSCSI protocol like security, high availability and so on.
    • Faster than iSCSI, FC, FCoE and easier to manage than SRP

     

    What are the requirements to deploy iSER?

    • Applications that can user SCSI and iSCSI layer
    • Network capable of passing RDMA
      • Adapter cards that supports RDMA (Ethernet of InfiniBand)
      • Ethernet switches (with Flow control or PFC)
      • InfiniBand switches
    • Target that supports iSER

     

    What storage targets supports iSER?

     

    What are the differences between TGT, LIO and SCST?

     

    TGTLIOSCST
    User spaceKernel space (in-tree)Kernel space (out-of-tree)
    iSER support since 2008iSER support since kernel 3.10iSER support since 2014
    Linux SCSI target framework (tgt) projectLinux SCSI TargetSCST: A Generic SCSI Target Subsystem for Linux

     

     

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    Storage Protocol Comparison

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    Storage ProtocoliSER (iSCSI RDMA)iSCSI (TCP)FCFCoESMB DirectNFSoRDMANVMe over Fabrics
    AccessBlockBlockBlockBlockFileFileBlock
    Transport (link protocol)Ethernet (RoCE), InfiniBandEthernetFCEthernetEthernet (RoCE), InfiniBandEthernet (RoCE), InfiniBandEthernet (RoCE), InfiniBand
    RDMAYesNoNoNoYesYesYes

     

     

     

    OpenStack Support

    iSER based on TGT target is inbox in OpenStack since Havana release.

    iSER data mover for OpenStack accelerates:

    • Storage access
    • VM migration
    • Data/VM replication

     

     

     

    iSCSI/iSER Architecture

    The transport layer iSER and/or iSCSI/TCP are transparent to the user. The configuration is simple.


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