Two iSCSI initiators to a single iSCSI target

Posted on 2011-10-24
Medium Priority
Last Modified: 2012-05-12
I am using
1. 2 x RHEL6 (iSCSI initiators A and B) connected to a single MD3000i  iSCSI storage.
2. A and B initiators belong to 1 Group
3. no CHAP, no passwords are set.
4. Both initiators A and B
 fdisk -l
Disk /dev/sdb: 5999.5 GB, 5999582773248 bytes
255 heads, 63 sectors/track, 729407 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1      267349  2147480811   83  Linux

4. mount /dev/sdb1 /iscsi

When I make changes on initiator A /iscsi directory,
initiator B does not see any changes and otherwise A does not see changes done by B.

I need to have both initiator to be able to read/write to a single target.
How I can make it happend with all changes being instantly visible by opposite initiator.
Is there any way to manipulate locking mechanism "persistent reservation" .

Thank you very much.
Question by:mbudman
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LVL 18

Accepted Solution

Andrej Pirman earned 1000 total points
ID: 37021753
AFAIK you are talking about MULTIPATHING driver, but you did not mention having it. You cannot have 2 clients r/w mode on same target store - filesystem does not have mechanism to know, which changes to listen to. You can render store unusable.
Mutlipath driver handles such situations. Install it on your Linux box.
LVL 56

Assisted Solution

andyalder earned 1000 total points
ID: 37029934
You can have multiple hosts accessing one iSCSI target with Linux, but you have to use a shared filesystem such as GFS. Additionally you need a distributed lock manager to stop both editing the same file at the same time.


Author Closing Comment

ID: 37132323
Good answer, although not necessarily what I was looking for,
Thanks for your assistance.


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LVL 56

Expert Comment

ID: 37132523
At least you just have to reformat with GFS, think about those poor Windows chaps who have to pay for a 3rd party filesystem.

Author Comment

ID: 37132584

Maybe you have a suggestion:

I have a SAN. solutions on the internet consist of configuring a third server to simulate a SAN. All I want is for the two Oracle RAC servers to read shared storage and update accoridingly.
LVL 56

Expert Comment

ID: 37132690
So from one of the Oracle servers format the iSCSI target using GFS, which is part of RedHat, then you have shared access. I think you'll have to upgrade to RedHat 6.1 or later though. http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/4/html/GFS_6.1_Administration_Guide/ch-install.html might help, I haven't set it up myself - not a Linux expert. Clicking next a few times on that link above to read subsequent pages tells how to do it though, looks straight forwards.
LVL 56

Expert Comment

ID: 37132792
Hmm, my bad, RedHat only needs to be 4.2, It's GFS that comes with it that's 6.1, and it does support iSCSI by the looks of it although I may be reading that wrong - http://www.centos.org/docs/4/html/rh-gfs-en-6.1/ch-overview.html 

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