[stgt] how to setup a virtual tape using scsi-target-utils?

ronnie sahlberg ronniesahlberg at gmail.com
Fri Jul 27 07:10:40 CEST 2012

I have fixed up wireshark to decode the luns properly in iscsi and
scsi layers.  It too did not understand the addressing modes :-)

On Thu, Jul 26, 2012 at 11:13 PM, Rob Evers <revers at redhat.com> wrote:
> On 07/25/2012 05:48 PM, Rob Evers wrote:
>> On 07/24/2012 11:44 PM, ronnie sahlberg wrote:
>>> Rob,
>>> This sounds like a bug in linux kernel/initiator.
>>> scsi: host 14 channel 0 id 0 lun16640 has a LUN larger than allowed by
>>> the host adapter
>>> LUN 16640   is in hex 0x4100    or split into addressing mode and lun
>>> Addressing mode is 01b   and the lun is 100h
>>> LUNs are specified as two bytes that is split into two parts.
>>> The two most significant bits is the addressing mode,   and the lower
>>> 14 bits have a different meaning depending on the mode.
>>> See SAM for more details.
>>> There are three different ways that luns>  256 can be represented :
>>> 00b : single lun level structure     where the next 6 bits would be
>>> the bus number,  and the lowest 8 bits would be the lun 0-255 on that
>>> bus.
>>> 11b : extended logical unit addressing, which is very complex and really
>>> weird.
>>> Or the one that TGTD uses :
>>> 01b : flat space addressing mode    where the low 14 bits are the lun
>>> number 0-8191
> One last note on this is that TGTD changes from single lun level structure,
> addressing mode 00b, to flat addressing mode 01b, when the lun number
> goes above 255.  This explains why the linux initiator code worked for the
> lower lun numbers.
> Rob
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