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

Rob Evers revers at redhat.com
Thu Jul 26 15:13:18 CEST 2012

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.

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