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Two iSCSI initiators to a single iSCSI target

Posted on 2011-10-24
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Last Modified: 2012-05-12
Hello,
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

Problem:
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.

Questions.
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.
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Question by:mbudman
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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.
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Assisted Solution

by:andyalder
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.

http://en.wikipedia.org/wiki/Global_File_System
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Author Closing Comment

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

Cheers,

Mark
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Expert Comment

by:andyalder
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.
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Author Comment

by:mbudman
ID: 37132584
Andy,

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.
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Expert Comment

by:andyalder
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.
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Expert Comment

by:andyalder
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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