Subject: iSCSI: Large Data Block Handling

From: "Kaladhar Voruganti" <[email-masked]>
Date: Mon, 25 Jun 2001 18:06:10 +0100

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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From: [email-masked] (Sandeep Joshi)
Date: Mon, 25 Jun 2001 13:52:52 -0400 (EDT)

it should be (b).
The iSCSI (i.e.transport) PDU size is not related to 
the SCSI request length.   

-sandeep

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From: "Martin, Nick" <[email-masked]>
Date: Mon, 25 Jun 2001 13:49:48 -0500

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: [email-masked]
[mailto:[email-masked]]
Sent: Monday, June 25, 2001 12:53 PM
To: [email-masked]; [email-masked]
Subject: Re: iSCSI: Large Data Block Handling

it should be (b).

-sandeep