ISCSI over a fible cable

I have an ISCSI attached QNAP storage device that I would like to place in a location that is 70 meters away as an off site storage. I have set up a 1 Gigabyte network link that consists of an ethernet patch cable from the server to a media converter to carry the link over the mutli core fibre then into a second media converter to a second ethernet patch cable into the QNAP device. Using TCP/IP the connection works perfectly, but when I attach the ISCSI connections the system fails. The server can see the QNAP over TCP/IP but cannot see it over ISCSI. Even the ISCSI initiator fails to see the target.
Can any one help me as to why this is so and what can I do about it?
Thanks in advance
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Gerald ConnollyCommented:
CAT-6 should be good for 70 meters at 1Gb
MikeinMackayAuthor Commented:
Unfortunatly I am unable to use CAT 6,  but there is a fibre cable already in place which I can use. I am trying to find out the reason it will not work with ISCSI but will work with TCP/IP. Thanks for the response though.
This doesn't make much sense. iSCSI uses TCP to get across the network.
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Gerald ConnollyCommented:
kevinhsieh, I agree, it sounds like the media convertors are not transparent?

@MikeinMackay, is there nothing except the cables and the media convertors between these two systems? no switches or anything?
MikeinMackayAuthor Commented:
The network is like this, The server connects to an ethernet patch that connects to the ISCSI switch (which all three of the ISCSI devices connect to and it is working with no issues). From the ISCSI switch, an ethernet patch cable connects it to a Hirschmann Spider II Giga media converter which sends it over a multi mode fiber optic cable to a second Hirschmann Spider II Giga media converter that feeds into an ethernet patch cable into the QNAP TS-879 Pro
device. all ethernet cables were tested using a Fluke cable tester and were ok. I have also tried matching Allied Telesyn media converters but with no luck. When I connect a laptop instead of the QNAP the connection on one side and the normal TCP/IP network on the other side the connection works fine. When I tested the system with-out the fiber optic and media converters the system worked fine.
I am  stumped on this any ideas would be greatfully appriciated.
I am generally stumped, but could there be a speed/duplex issue between the switch and the QNAP, or maybe a crossover issue?

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MikeinMackayAuthor Commented:
We have decided to abandon using ISCSI in this situation as we tried but failed to get the system to work. I would like to thank all you contributed to a solution.
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