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    "Lower overhead" iSCSI

    Let me start off by saying that I am interested in doing "iSCSI" protocol
    over UDP.  Now I realize that this is an old issue and will probably start
    some "religious" battles, but let me state the scenarios before I receive
    death threats.  The planned environment that this will go into is a small
    one with say 10 servers connected through a "non-blocking" switch to the
    storage device (ie no routers, gateways, etc...just direct point-to-point
    connections).  This is assuming that the switch is really non-blocking and
    hopefully implements flow control or pause frames.  So technically all you
    should have to worry about is port/device contention.  However, when you
    think about it...this is similar to FC.  FCP runs on class 3 FC which is a
    non-reliable transport protocol such as UDP and handles contention, also
    some of the early "SAN interconnect" guys are doing this today with
    relatively good performance and few issues.
    	The attempt here is to maintain low CPU utilization at high
    performance rates.  While I realize that these TOE devices are moving along
    rapidly, there are some situations where they are not feasible, such as a
    blade server environment (no PCI slots, and no real estate/power available
    for onboard TOE).  Worst case scenario is that a packet is dropped or
    received out of order and the ULP (SCSI) must resend the cmd/data sequence -
    still no data lost, just a temporary performance hit.
    	So my question is:  is this feasible?, and why not implement an
    "iSCSI" protocol layer that can run over TCP or UDP(though I realize it
    won't be considered "standards compliant")?


Last updated: Wed Jan 30 02:17:58 2002
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