From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bryant G. Ly" Date: Tue, 24 Apr 2018 12:53:53 +0000 Subject: Re: MaxTransferLength Message-Id: <6e1343a2-907e-4467-d6d1-ae614ba2d486@linux.vnet.ibm.com> List-Id: References: <20180424122512.GQ27687@hydro.skol.ch> In-Reply-To: <20180424122512.GQ27687@hydro.skol.ch> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: target-devel@vger.kernel.org On 4/24/18 7:38 AM, Hannes Reinecke wrote: > On 04/24/2018 02:25 PM, Nicolas D wrote: >> >> 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. >> > > 'pscsi' is the SCSI pass-through, so it'll be presenting the values > from the underlying device; I doubt you can change that. > > What you could try is to mount the DVD, and export the mountpoint via > the file backend; that way you should be able to tweak the parameters. > > Adding to what Hannes is saying, if you need true dvd/cd emulation you can use file optical media backstore via user:fbo from tcmu-runner. Bryant