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    RE: iSCSI: Large Data Block Handling



    To emphasize Sandeep's point.
    
    iSCSI PDU size does not limit the amount of data which can be transferred
    with a single SCSI CDB.
    However, both the initiator and the target must respect DataPDULength on all
    PDU's.
    If the current negotiated value is 8K then the initiator must break up write
    data and the target must break up read data into multiple PDU's each
    carrying no more than 8K of data.  The target also is allowed to request
    more than 8K of write data with a single R2T, but the data is expected to be
    delivered by multiple PDU's whenever required.
    
    Thanks,
    Nick
    -----Original Message-----
    From: sandeepj@research.bell-labs.com
    [mailto:sandeepj@research.bell-labs.com]
    Sent: Monday, June 25, 2001 12:53 PM
    To: ips@ece.cmu.edu; kaladhar@us.ibm.com
    Subject: Re: iSCSI: Large Data Block Handling
    
    
    it should be (b).
    The iSCSI (i.e.transport) PDU size is not related to 
    the SCSI request length.   
    
    -sandeep
    
    > I would like some opinions on the following issue:
    > 
    > When the initiator and the target negotiate an agreed upon PDU max size
    > (say 8K), and if the initiator receives a larger sized read request (say
    > 64K), then
    > 
    > a) Should the initiator chop the large 64K size request into smaller 8K
    > sized requests and send these to the target
    > 
    > OR
    > 
    > b) The initiator sends the 64K request to the target and the target sends
    > only 8K responses to the initiator.
    > 
    > 
    > 
    > Kaladhar
    


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Last updated: Tue Sep 04 01:04:24 2001
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