iscsi target on a zfs zvol?

[Hauke Fath <hauke%Espresso.Rhein-Neckar.DE@localhost>]

Hi,

I would like to set up an iscsi target backed by a zfs zvol, to serve 
as a Mac time machine volume.

But the attempt to start the target fails with

 # /etc/rc.d/iscsi_target onestart
Starting iscsi_target.
Reading configuration from `/etc/iscsi/targets'
target0:rw:0.0.0.0/0
        extent0:/dev/zvol/rdsk/tank/time_machine_1:0:0
DISK: 1 logical unit (0 blocks, 512 bytes/block), type iscsi fs
DISK: LUN 0: pid 
863:/u/sources/netbsd-developer/src/external/bsd/iscsi/lib/../dist/src/lib/disk.c:720: 
***ERROR*** error reading "target0"
pid 
863:/u/sources/netbsd-developer/src/external/bsd/iscsi/lib/../dist/src/lib/disk.c:886: 
***ERROR*** error allocating space for "target0"
pid 
863:/u/sources/netbsd-developer/src/external/bsd/iscsi/lib/../dist/src/lib/target.c:1990: 
***ERROR*** device_init() failed
iscsi_target_start() failed
#

until I do something like

# hexdump -C -n 512 /dev/zvol/rdsk/tank/time_machine_1 
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  
|................|
*
000001b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 fe  
|................|
000001c0  ff ff ee fe ff ff 01 00  00 00 fe ff ff ff 00 00  
|................|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  
|................|
*
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  
|..............U.|
00000200
#

at which point

 # /etc/rc.d/iscsi_target onestart
Starting iscsi_target.
Reading configuration from `/etc/iscsi/targets'
target0:rw:0.0.0.0/0
        extent0:/dev/zvol/rdsk/tank/time_machine_1:0:2199023255552
DISK: 1 logical unit (4294967296 blocks, 512 bytes/block), type iscsi fs
DISK: LUN 0: 2097152 MB disk storage for "target0"
TARGET: iSCSI Qualified Name (IQN) is 
iqn.1994-04.org.netbsd.iscsi-target
#

Looks like an initialization issue on behalf of iscsi-target. Does that 
ring a bell for anyone?

Cheerio,
Hauke

-- 
Hauke Fath                        <hauke%Espresso.Rhein-Neckar.DE@localhost>
Linnéweg 7
64342 Seeheim-Jugenheim
Germany