tgt needs restart to find LUN

[Dave Gilbert]

I've got a KVM guest running Quantal server (as per CD install 2012-09-01) and it runs tgtd with a single target
(the target is an LVM lv - I'll attach any configs that apport hasn't attached)

If I just boot the vm, the guests don't see the disc - when they log in they just see the 'controller' (LUN 0),
if I restart tgtd then they see the disc (LUN 1).

I've edited /etc/init/tgt.conf to add the flag to specify two portals and to turn on debug.

Dave

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: tgt 1:1.0.17-1ubuntu2
ProcVersionSignature: Ubuntu 3.5.0-13.14-generic 3.5.3
Uname: Linux 3.5.0-13-generic x86_64
ApportVersion: 2.5.1-0ubuntu4
Architecture: amd64
Date: Sat Sep 8 21:55:14 2012
InstallationMedia: Ubuntu-Server 12.10 "Quantal Quetzal" - Alpha amd64 (20120901)
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: tgt
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.init.tgt.conf: 2012-09-08T21:51:30.593039

[Dave Gilbert (ubuntu-treblig)]

This is the tgt conf that specifies the target:

root@server1:/var/log# cat /etc/tgt/conf.d/dag.conf

# Sample target with one LUN only. Defaults to allow access for all initiators:
#
#iSNSServerIP 192.168.122.10
#iSNSServerPort 3205
#iSNSAccessControl On
#iSNS On

<target iqn.2008-09.com.example:server1.share1>
    backing-store /dev/mapper/server1-share1
</target>

[James Page (james-page)]

Hi Dave

Do you see any output during first boot which would indicate why tgt does not present the LUN? I think this may be some sort of race condition between tgt startup and the device mapper having detected all devices.

It would be good if you could also try using a file as a backing-store to see if you get the same problem.

[James Page (james-page)]

Dave

I've not been able to reproduce your issue using a quantal KVM instance.

Please could you run:

   sudo tgtadm --lld iscsi --mode target --op show

when you see the issue - hopefully this will tell us a bit more.

Thanks

[Dave Gilbert (ubuntu-treblig)]

Hi James,
  I agree it's likely to be an lvm/udev race; some observations:
     1) It doesn't seem to happen with files
     2) With lvm, It doesn't always happen if the guest is configured with a single core; most of the time but not always
     3) With lvm it seems to happen (almost?) always when the guest has multiple cores.

output of tgtadm as requested:

----- lvm based, bad ---

Target 1: iqn.2008-09.com.example:server1.share1
    System information:
        Driver: iscsi
        State: ready
    I_T nexus information:
        I_T nexus: 1
            Initiator: iqn.2005-03.org.open-iscsi:2b2883cd283
            Connection: 0
                IP Address: 192.168.123.12
        I_T nexus: 2
            Initiator: iqn.2005-03.org.open-iscsi:2b2883cd282
            Connection: 0
                IP Address: 192.168.122.12
    LUN information:
        LUN: 0
            Type: controller
            SCSI ID: IET 00010000
            SCSI SN: beaf10
            Size: 0 MB, Block size: 1
            Online: Yes
            Removable media: No
            Readonly: No
            Backing store type: null
            Backing store path: None
            Backing store flags:
    Account information:
    ACL information:
        ALL

--- LVM based, after restarting tgt ---

Target 1: iqn.2008-09.com.example:server1.share1
    System information:
        Driver: iscsi
        State: ready
    I_T nexus information:
        I_T nexus: 1
            Initiator: iqn.2005-03.org.open-iscsi:2b2883cd283
            Connection: 0
                IP Address: 192.168.123.12
        I_T nexus: 2
            Initiator: iqn.2005-03.org.open-iscsi:2b2883cd282
            Connection: 0
                IP Address: 192.168.122.12
        I_T nexus: 3
            Initiator: iqn.2005-03.org.open-iscsi:2b2883cd283
            Connection: 0
                IP Address: 192.168.123.12
        I_T nexus: 4
            Initiator: iqn.2005-03.org.open-iscsi:2b2883cd282
            Connection: 0
                IP Address: 192.168.122.12
    LUN information:
        LUN: 0
            Type: controller
            SCSI ID: IET 00010000
            SCSI SN: beaf10
            Size: 0 MB, Block size: 1
            Online: Yes
            Removable media: No
            Readonly: No
            Backing store type: null
            Backing store path: None
            Backing store flags:
        LUN: 1
            Type: disk
            SCSI ID: IET 00010001
            SCSI SN: beaf11
            Size: 10737 MB, Block size: 512
            Online: Yes
            Removable media: No
            Readonly: No
            Backing store type: rdwr
            Backing store path: /dev/mapper/server1-share1
            Backing store flags:
    Account information:
    ACL information:
        ALL

(can also see the client accessing it there)

--- file based, good ---

Target 1: iqn.2008-09.com.example:server1.share1
    System information:
        Driver: iscsi
        State: ready
    I_T nexus information:
        I_T nexus: 5
            Initiator: iqn.2005-03.org.open-iscsi:2b2883cd283
            Connection: 0
                IP Address: 192.168.123.12
        I_T ...

[Тимофей (nefelim4ag)]

tgt-admin -e
for updating configuration