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iscsi target

Posted on 2015-02-16
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Last Modified: 2015-02-27
I am trying to add this target to three ESXi hosts.

I was able to add to .32 but not others. i wonder why?


<target iqn.2015-02.com.example:target00>
        backing-store /dev/sanvg/sanlv
        initiator-address 192.168.1.32
        initiator-address 192.168.1.53
        initiator-address 192.168.1.55
</target>
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Question by:linuxperson
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10 Comments
 
LVL 78

Assisted Solution

by:arnold
arnold earned 333 total points
ID: 40614395
A LUN should only be accessed by one HOST At a time.

iscsi is SCSI (low level commands) over IP.  This means that data corruption is likely.
Host A writes, HOST B and HOST C are not informed of this change and will not see what is written, They can then each write something different of which the others will not be aware and could overwrite/use the same space on which others have written.

Look at the LUN configuration dealing with access rights.
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Author Comment

by:linuxperson
ID: 40614867
I understand the i need a some kind of cluster file system to be able to manage this.

However  i just wanted to know how to allow multiple hosts to see this LUN
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LVL 78

Expert Comment

by:arnold
ID: 40614898
What are you trying to do?  There are other ways of providing access to a shared resource, but it all depends on the manner in which that resource is needed.
you could the ISCSI LUN mounted by one system and have it shared so the others can access it.
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Author Comment

by:linuxperson
ID: 40614910
<target iqn.2015-02.com.example:target00>
        backing-store /dev/sanvg/sanlv
        initiator-address 192.168.1.32
        initiator-address 192.168.1.53
        initiator-address 192.168.1.55
</target>

will this work?
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LVL 78

Expert Comment

by:arnold
ID: 40614933
Where is this ?  Not sure you've changed anything?
you can have IP 192.168.1.32 mount the iscsi lun.
And then turn around and export it as an NFS share.
This way all systems can read and write to the same LUN with the system on 192.168.1.32 functioning as the arbitrator and sole direct writer into the LUN.

The use of an ISCSI lun might not be necessary in your situation where an NFS share or other types are as suitable.

Are the three hosts you reference part of a cluster?
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Author Comment

by:linuxperson
ID: 40615021
Are you talking about vmware cluster?
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Author Comment

by:linuxperson
ID: 40615031
I think its wrong example i am asking.  I understand file system corruption and other things you explained me here.

all I am trying to test is if all three ESXi hosts can see this iSCSI target according to below definition.

<target iqn.2015-02.com.example:target00>
        backing-store /dev/sanvg/sanlv
        initiator-address 192.168.1.32
        initiator-address 192.168.1.53
        initiator-address 192.168.1.55
</target>
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LVL 78

Accepted Solution

by:
arnold earned 333 total points
ID: 40615037
No, the issue with an ISCSI resource is that it can only be accessed by one device at a time to avoid data corruption.
It does not matter what your intended use of the iscsi LUN is, only one host should be connected to it at one time.

VMWARE cluster, or guest OS cluster, it all depends to which portion of your setup this LUN is allocated.
VMWARE host (only one can connect)
VMware guest OS, only this guest can connect to it)
you can have VMWARE host access the LUN and then make it available to the Guest VMs.

You are not providing the inforamtion on what you have and are dealing with to see whether you actually need to use an ISCSI resource or another type might be as well or better suited for your needs.
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LVL 78

Expert Comment

by:arnold
ID: 40615049
Use each host, go through the iscsi discovery and see whether this LUN is presented to it.  The only test is to actually try to mount it which means you should go to host 192.168.1.32 explore the iscsi host for targets and connect to this target.  once successful disconnect.
Go to the next host and repeat.

If one works, they all should work.
Verify IP addresses.

Is the VMWARE host the iscsi host, or is the SAN on a lan, in which case you have to make sure that the IPs of the guest  Vms are on the lan as well.
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LVL 20

Assisted Solution

by:compdigit44
compdigit44 earned 167 total points
ID: 40617812
Hi linuxperson, if I am understand you correctly you want to take three host and have all of them access the same LUN/datastore correct????

What are you using for the iscsi target server?
Can you upload some screen shot of your config...

The following link reference to iSCSi FreeNas will multiple host and should like the person was successful..

https://forums.freenas.org/index.php?threads/sharing-iscsi-with-multiple-esxi-5-1.15558/
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