Andrey Kuzmin wrote:
> IIRC (it's over a years since I last looked at user-space iSCSI target
> code), iscsit supports pass-through mode so that running local tape
> target should not be a problem. Of course, whether such a mode was
> envisaged/designed for is a totally different question.
>
> Regards,
> Andrey
>
The problem is that iscsitgtd sends SCSI commands to the backing device on its
own in raw mode during initialization phase. This is an excerpt from iscsitadm
man page:
......... raw indicates
that the emulator will use the uSCSI interface and pass
the command blocks directly to and from the device. The
use of raw also implies the option --backing-store will
be entered. The argument to this option is the full
pathname to the device node normally found in /dev. If
you use --backing-store, the size of the store is deter-
mined by a SCSI READ_CAPACITY command or, if the backing
store is a regular file, by stat(2).
The consequence of the text above is that tape device can't be used as a backing
store even in raw mode. The READ_CAPACITY which is always sent to the device is
a block device specific command and fails with sense key 0x5 (Illegal Request)
when sent to a tape.
It seems that the iscsitgtd was not designed for tape backing at all.
Regards,
Milos
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