From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nicolas D <nd@saitis.net>
Date: Tue, 24 Apr 2018 12:25:19 +0000
Subject: MaxTransferLength
Message-Id: <20180424122512.GQ27687@hydro.skol.ch>
List-Id: <target-devel.vger.kernel.org>
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To: target-devel@vger.kernel.org


Hello everyone,

I tried googling a lot about this problem, but I had no luck till now.

I am having some trouble to read from a dvd/bd drive that is configured
with targetcli with pscsi driver on different not so old linux versions:
 - debian (version: saddly don't have the computer with me and don't
   remember exactly but should be Jessie)
 - ubuntu (14.04/kernel 3.13)

The problem is the same with all the initiator/os I could play with:

- Core-iSCSI/Linux
- MS-initiator/Windows
- StarWind/Windows
- Sns GlobalSan/MacOS

The actual problem is that my target don't react well when the initiator
ask to read more than 16KB in one read instruction: the response is a
sense error or unit error (error discovered in pcap trace, thanks to
wireshark).

I could lower the MaxTransferLength with the "MS-initiator/Windows" and
for that initiator/os it works now perfectly.

https://support.zadarastorage.com/hc/en-us/articles/213024226-Recommended-Windows-iSCSI-initiator-Registry-configuration

But Sns GlobalSan for example does not support limiting read size on is
side, and I think it's definitively the target that has to tell the
initiator about this MaxTransferLength attribute, or I may be wrong?

I tried to tweak some parameters with targetcli, but:
- lowering fabric_max_sectors does not seem to help
- hw_max_sectors%6 hw_block_size 48 are read-only

I have definitively trouble finding documentation on all other
backend attributes.

I have the impression that my problem is more config related, it's why I
did not took the time to write all exact versions of the os/tools I use.

If you think I am wrong, I'll provide all useful informations.

Thank you for your help and for all the job already made to have this
iscsi stack working in linux.

Nicolas