I’ve been looking at this for a couple of days and here are my findings.The above tutorial is great if you have only one target iSCSI volume. If you have multiple targets to connect to, there are a few things to consider.

1. When the targets are discovered, they wont be discovered in the same order you set them up on your storage server.
2. When you reboot the server or restart iSCSI, the targets will not always be assigned the same device names each time.
3. The order in which the targets are discovered by the iscsi service, is not neccessarily the order in which they are assigned device names – so dont assume that each discovered node will be assigned /dev/sdb, /dev/sdc, /dev/sdd in turn – they wont.

So, it is extremely difficult (or impossible) to identify which target volume applies to what device name If you enable all your targets at the same time and discover them all at once. To overcome the above issues you simply need to set up, discover and configure each target volume one at a time – then label the partitions and mount them using the label, instead of the device name. Here is how I did it…

1. Create the first iSCSI target on your storage server. On some devices you will be able create all of them and set all but one to disabled for now. I’m using a Thecus N8800. I have 12TB split into 8 iSCSI volumes. The important thing at this step is to ensure that you only have your first iSCSI target enabled for discovery.

2. Follow the instructions in “Step # 1: Configure iSCSI” and “Step # 2: Discover targets” in the main tutorial above.

Side note: I am yet to understand the node.session. and discovery.sendtargets. authentication options. On my storage device I have the option to create a CHAP username and password for each target but I dont know how this equates to either node.session. or discovery.sendtargets. or how to set this up in the config file for multiple targets with different usernames. So I currently have the CHAP authentication disabled completely.

3. From fdisk-l note the device name and give it a label…

# e2label /dev/sdb1 iscsi001

4. Enable the second iSCSI target on your storage device and run the first step from “Step # 2: Discover targets” in the above tutorial…

# iscsiadm -m discovery -t sendtargets -p 192.168.x.x
# /etc/init.d/iscsi restart

5. When you run fdisk-l now, you will see your first target volume has been renamed to /dev/sdc1 and your new one has taken its place as /dev/sdb1.

Complete your partioning and formatting of the new volume and then label it…

# e2label /dev/sdb1 iscsi002

Of course, the labels will remain, no matter what the device name. So if you read the label…

# e2label /dev/sdc1

the response will be…

iscsi001

# e2label /dev/sdb1

iscsi002

Repeat all the above steps for all your targets so that each one has a device label.

Now mount the target volumes using the label instead of the device name…

mkdir /mnt/iscsi001;
mkdir /mnt/iscsi002;
mkdir /mnt/iscsi003;
mkdir /mnt/iscsi004;

In /etc/fstab

LABEL=iscsi001 /mnt/iscsi001 ext3 _netdev 0 0
LABEL=iscsi002 /mnt/iscsi002 ext3 _netdev 0 0
LABEL=iscsi003 /mnt/iscsi003 ext3 _netdev 0 0
LABEL=iscsi004 /mnt/iscsi004 ext3 _netdev 0 0

From the command line

mount -L iscsi001 /mnt/iscsi001

Hope this helps anyone else who has the same dilemma :-)

I want to ensure that these are connected the same way each time. I see no way in the config file to specify each target – it seems to just auto discover. I dont want to auto discover. How can I specify the target’s target name or iqn so that it always gets the same device name each time? The device name appears to be dynamically created on boot. What happens if it dicovers one device before another next time it boots? will it apply a different device name to the one before. I need to be able to specify this somehow.

On the storage device config I can choose a target name and a CHAP username and password for each target – each has their own iqn. I cant work out how to use CHAP authentication to conenct to four seperate targets. The config file only has an option to specify one username and password and there is no way of specifying the target. It doesnt make sense.

I need to do the following…

1. When the iscsi service is started, connect to four target devices using a different CHAPS username and password for each one.
2. Ensure that each device always has the same device name.

If somoene could point me in the direction of a tutorial or docuement that shows specifically how to do this I would be very grateful. Thank you for your time.

I did not use partition anymore. I was able to mount and umount the iscsi and use it for 19 days now w/o a problem.

Chris:,
Do you really need to restart the server? How about just restarting the iscsi sevices?

Rgds,
Jay A

It works perfectly 99% of the time but my problem is if I lose connection to the target for any reason, if iscsi is restarted, or if the volume is unmounted, the only way to get it to work properly again is to reboot the server. It doesnt seem as reliable as people say.

HTH

Regards Majk

[root@cent ~]# iscsiadm -m discovery -t sendtargets -p 192.168.2.0
iscsiadm: cannot make connection to 192.168.2.0:3260 (101)
iscsiadm: connection to discovery address 192.168.2.0 failed
iscsiadm: cannot make connection to 192.168.2.0:3260 (101)
iscsiadm: connection to discovery address 192.168.2.0 failed
iscsiadm: cannot make connection to 192.168.2.0:3260 (101)
iscsiadm: connection to discovery address 192.168.2.0 failed
iscsiadm: cannot make connection to 192.168.2.0:3260 (101)
iscsiadm: connection to discovery address 192.168.2.0 failed
iscsiadm: cannot make connection to 192.168.2.0:3260 (101)
iscsiadm: connection to discovery address 192.168.2.0 failed
iscsiadm: connection login retries (reopen_max) 5 exceeded

I tried service iscsi restart; service iscsid restart and tried the command again but I still am not able to connect to it. Did I configure the vi /etc/iscsi/iscsid.conf correctly?

# to CHAP. The default is None.
node.session.auth.authmethod = CHAP

# To set a CHAP username and password for initiator
# authentication by the target(s), uncomment the following lines:
node.session.auth.username = [our username goes here]
node.session.auth.password = [our password goes here]

# To set a CHAP username and password for target(s)
# authentication by the initiator, uncomment the following lines:
node.session.auth.username_in = [our username goes here]
node.session.auth.password_in = [our password goes here]

# To enable CHAP authentication for a discovery session to the target
# set discovery.sendtargets.auth.authmethod to CHAP. The default is None.
#discovery.sendtargets.auth.authmethod = CHAP

# To set a discovery session CHAP username and password for the initiator
# authentication by the target(s), uncomment the following lines:
#discovery.sendtargets.auth.username = username
#discovery.sendtargets.auth.password = password

# To set a discovery session CHAP username and password for target(s)
# authentication by the initiator, uncomment the following lines:
#discovery.sendtargets.auth.username_in = username
#discovery.sendtargets.auth.password_in = password

Thanks,
Eric Averitt

My iscsi volume is 5GB on a RAID5 array. I could find no way to sucessfully partition this so I simply formatted the whole volume. When I do fdisk -l I get “Disk /dev/sdb doesn’t contain a valid partition table” but this doesnt seem to be a major issue.

When I start up the server, iscsi finds the target, /dev/sdb is created and then mounted via fstab. I can connect to the volume fine.

If I restart iscsi for any reason, I lose the disk – it disappears and is re-detected as /dev/sdc instead.

I am also unable to unmount it without getting “device is busy”.

Any ideas?

This is how it looks like when I issue fdisk -l

Disk /dev/sdn: 143.0 GB, 143034155008 bytes
255 heads, 63 sectors/track, 17389 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdn1 1 17389 139677111 83 Linux

Disk /dev/sdn1: 143.0 GB, 143029361664 bytes
255 heads, 63 sectors/track, 17388 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdn1 doesn’t contain a valid partition table

Disk /dev/sdo: 968.0 GB, 968016265216 bytes
255 heads, 63 sectors/track, 117687 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdo1 1 117687 945320796 83 Linux

The one with the problem is /dev/sdo1. I’m expecting it to be looked like sdn1.
(sdo1 and sdn1 are partition of sdo and sdn device).

I am using rhel 4 AS, 2.6.9-42ELsmp,

iscsitarget-kernel-smp-0.4.12-6_2.6.9_42.EL
iscsitarget-0.4.12-6
iscsi-initiator-utils-4.0.3.0-4

Regards,
Jay A

real 0m24.005s
user 0m0.000s
sys 0m0.000s
##########
0+10 enregistrements lus.
0+10 enregistrements écrits.

real 0m0.001s
user 0m0.000s
sys 0m0.001s
##########
0+10 enregistrements lus.
0+10 enregistrements écrits.

real 0m0.001s
user 0m0.000s
sys 0m0.001s
##########
0+9 enregistrements lus.
0+9 enregistrements écrits.

real 0m0.535s
user 0m0.000s
sys 0m0.001s

I do not know why sometime the response time is very long

Thx

I had the same error, chkconfig showed me that they were on – but a reboot of the clients solved my problems

stujap

Maybe stupid question, but i don’t undertand where i can find or set initiator name? Or i don’t need it? What should i set on storage site?

Thank you,
Jap