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Problem, in short: I'm having trouble sharing a datastore between two virtual esxi6.5 hosts on a common ISCSI Lun exposed to them. Only one of them is able to create while other one loses its datastore.

Details: I have two Esxi6.5 virtual machines (say H1 and H2) running on Ubuntu as the host OS. On Ubuntu, I created a ISCSI lun and exposed to both H1 and H2. Problem comes when I try to make a datastore on the ISCSI LUNs through each Esxi Host. With the datastore created on the ISCSI LUN through H1, if i try to share the same data store to H2 it fails saying "no device found with free space". Even if somehow it shows me the ISCSI lun and when I create the datastore over it, the other host loses its data store.

What do I need to do to H1 and H2 to make them share?

  • Firstly why are you running 2 x ESXi VMs??? also why are you trying to make the datastore on both virtual-ESXi VMs? You should expose the LUN to both machines, then create the datastore on one of them then refresh the storage of the second, it'll just see the partition and mount the VMFS volume, you only do this once on one machine. – Chopper3 Feb 23 '18 at 9:07
  • Thanks Chopper for the reply. I need to do some sort of experimentation on such a setup. When you create the datastore on one of them, then you say that if i simply rescan the devices, it would show me the data store added to the list of datastores for the second host ? let me do that – Kapil Feb 23 '18 at 9:57
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    No, thats not happening. I just created the datastore on the LUN through H1. Refreshed the datastores on the second. Nothing happened. – Kapil Feb 23 '18 at 11:21
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    Chopper3, I was able to do it finally. Today also, i just refreshed the devices and the Datastore was mounted on the second host. I am not sure I am wrong in doing something of GUI is buggy. Yesterday, I did exactly the same thing but no results. Thanks for your suggestion, it helped me a lot. – Kapil Feb 24 '18 at 5:58
  • No problem, still no idea why you're doing this glad you're good – Chopper3 Feb 24 '18 at 10:31
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It's most possible SCSI Persistent Reservations are either disabled or not supported by your iSCSI target.

http://linux-iscsi.org/wiki/Persistent_Reservations

What target do you use?

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Possibly your iSCSI target doesn't support multi-host access (this requires atomic read-modify-write) or the access ACLs on the target are incorrect (you need to map the LUN the both hosts).

  • Will try to find out how to check if multi host write is a possibility or not. Regarding ACL. I can create the data store on the same lun independently. i.e both the hosts can create a exclusive datastore. Its the sharing thats the problem. So I think ACL should not be an issue. Agree ? – Kapil Feb 23 '18 at 12:26
  • You only create a single LUN and then map it to both hosts, allowing read/write access. – Zac67 Feb 23 '18 at 13:11
  • There is a single lun here. Both the hosts access it. – Kapil Feb 23 '18 at 16:22

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