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This tip explains how to create, manage iSCSI volumes (including LVM managed) on SLES 10 SP1 then mount them automatically at reboot.

Problem:

Unfortunately the documentation doesn't discuss this matter well and it gets really tricky when you have a large volume and want to manage it with LVM.

Solution:

I shall demonstrate the solution with an assumption that you have some SLES, iSCSI knowledge already and you have a system installed with mainly default settings.

1. Open-iSCSI software installation and configuration

geeko:~ # yast2 sw_single

Click to view.

When finished, find out your generated initiator id:

geeko:~ # grep . /etc/iscsi/initiatorname.iscsi | grep -v ^#
InitiatorName=iqn.1996-04.de.suse:01.df9759e0f317

Now you have to get your storage allocated in the iSCSI system as well so let your iSCSI admin know your IP address, hostname and the generated initiator id above. Once it's ready, configure your client:

geeko:~ # yast2 iscsi-client &

Click to view.

Select “When Booting” at the first tab.

Click to view.

At the second tab enter either the IP address (preferred) of your iSCSI array or its DNS name, leave the port default. I don't have authentication set therefor it's selected also.

Click to view.

Go to the third tab then select “Discovery”. If you did everything right (and of course your storage is set in iSCSI as well) it should find your allocated storage area. Select each of them then “Log In”.

Now switch back to the second tab:

Click to view.

On the second tab select each target then “Toggle Start-Up” which will cause the targets set to automatically come up at next reboot. At completion click “Finish”.

2. LVM2 over iSCSI

I have a large 5T storage area allocated therefor I am forced to use LVM2 due to traditional Linux partitions cannot be larger than 2T. If you won't use LVM2 then you can skip this section and jump to step 3. right now.

My storage area is split up as 2x2TB and 1x1TB so I have 3 devices under dev:

geeko:~ # ls /dev/sd*
sda  sdb  sdc

I set up LVM from the command line:

geeko:~ # pvcreate /dev/sda /dev/sdb /dev/sdc

After initializing the disks set up a volume group:

geeko:~ # vgcreate iscsigroup1 /dev/sda /dev/sdb /dev/sdc

Once done, we can create logical volume:

geeko:~ # lvcreate -L5T -n iscsi_volume1 iscsigroup1

Find out the device mapper ID for the new LVM volume:

geeko:~ # lvdisplay /dev/iscsigroup1/iscsi_volume1
  --- Logical volume ---
  LV Name                /dev/iscsigroup1/iscsi_volume1
  VG Name                iscsigroup1
  LV UUID                CYmaJw-gRdv-9LIi-ULPU-2PTX-cxup-c70TNE
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                5.00 TB
  Current LE             1310717
  Segments               3
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:0
  
  

What matters here is the last line 253:0 which tells us that the DM number is 0. It's required to find out the device's uuid what we will use to mount the volume at boot. The device what we will need to query is /dev/dm-<number> which is dm-0 in my case.

3. Set up fstab

Find out the uuid of your new LVM2 volume:

geeko:~ # udevinfo -q symlink -n /dev/dm-0
disk/by-uuid/de9f51df-2375-4e83-947b-b5b7f4126db2

Users who didn't need LVM2 can just do the same for their device for instance sda1, sdb3, etc.
The correct fstab entry after all:

geeko:~ # vi /etc/fstab
-snip-
/dev/disk/by-uuid/de9f51df-2375-4e83-947b-b5b7f4126db2  /mnt/iscsi xfs    hotplug            0 2

Explanation:

We need to insert “/dev/” in front of to the uuid we retrieved and use “hotplug” option instead of “_netdev”. To read more about this please visit this page:
http://en.opensuse.org/Open-iSCSI_and_SUSE_Linux

I recommend xfs filesystem on LVM2 volumes because it allows you to grow it even online.

Now the system is supposed to be set for users not using LVM2 over iSCSI and ready for reboot but at compilation we ensure that the necessary services are set for startup:

geeko:~ # chkconfig -l open-iscsi
open-iscsi                0:off  1:off  2:off  3:on   4:off  5:on   6:off

4. LVM discovery on iSCSI volumes at startup

Unfortunately when iSCSI was added to SLES10, LVM discovery was not considered in the design. It exists in bugzilla as defect 254723 but there will be no fix for it as it's a feature.
However I was assured by the support team that it has been accepted as feature upgrade in the upcoming releases SLES11 and for SLES10 SP2 also hence the solution I am providing here is just “for the time being” and should not be used after SP2.

I backed up the original init script then created a patch:

geeko:~ # cp /etc/init.d/open-iscsi /etc/init.d/open-iscsi.dist
geeko:~ # cat /etc/init.d/open-iscsi.patch
--- open-iscsi.dist     2007-08-03 04:55:31.000000000 +1200
+++ open-iscsi  2007-12-10 16:38:15.000000000 +1300
@@ -23,11 +23,15 @@
 # Source LSB init functions
 . /etc/rc.status

+# Source LVM configuration
+. /etc/sysconfig/lvm
+
 # Reset status of this service
 rc_reset

 iscsi_login_all_nodes()
 {
+       /bin/sleep 4
        echo -n "Setting up iSCSI targets: "
        $ISCSIADM -m node --loginall=automatic
        rc_status -v
@@ -94,6 +98,17 @@
     done
 }

+iscsi_scan_lvm_nodes()
+{
+    #
+    # Find and activate iSCSI volume groups
+    #
+    echo "Scanning for iSCSI LVM volume groups..."
+    /sbin/vgscan --mknodes
+    echo "Activating iSCSI LVM volume groups..."
+    /sbin/vgchange -a y $LVM_VGS_ACTIVATED_ON_BOOT
+}
+
 case "$1" in
     start)
        [ ! -d /var/lib/iscsi ] && mkdir -p /var/lib/iscsi
@@ -109,6 +124,9 @@
        fi
        if [ "$RETVAL" == "0" ]; then
            iscsi_login_all_nodes
+           iscsi_scan_lvm_nodes
+           /bin/sleep 2
+           /bin/mount -a > /dev/null 2>&1
        fi
        ;;
     stop)
	 
	 

Save it somewhere, perhaps at the same location then apply it:

geeko:~ # cd /etc/init.d
geeko:/etc/init.d # patch -p0 < open-iscsi.patch

The system is ready and should mount your iSCSI volumes at next reboot.

Environment:

SLES10SP1
open-iscsi-2.0.707-0.24