iSCSI sharing between two separately managed clusters

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Hi,

 

Just after a bit of advise regarding sharing iSCSI LUN’s between ESXi clusters (separate vCenters). This is a very basic overview of my setup:

 

+————————————–+       +————————————–+

| VCENTER1                             |       | VCENTER2                             |

| +———-+ +———+ +———+ |       | +———-+ +———+ +———+ |

| | ESXI1    | | ESXI2   | | ESXI3   | |       | | ESXI4    | | ESXI5   | | ESXI6   | |

| +—–|—-+ +—-|—-+ +—-|—-+ |       | +—–|—-+ +—-|—-+ +—-|—-+ |

+——-|———–|———–|——+       +——-|———–|———–|——+

        |           |           |                      |           |           |

         |———–+———–+———————-+———–+———–+

        |

+——-|——————————+

| QNAP ISCSI target                    |

| +———-+ +———+ +———+ |

| | LUN_0    | | LUN_1   | | LUN_2   | |

| | VMFS1    | | VMFS2   | | VMFS3   | |

| +———-+ +———+ +———+ |

+————————————–+

 

My intentions are for hosts ESXI1/2/3 (i.e. VCENTER1 cluster) to share LUN_0 and for hosts ESXI4/5/6 (i.e. VCENTER2 cluster) to share LUN_1 & LUN_2

 

My concern is all 6 hosts automatically attach all 3 LUNS (and mount associated VMFS volumes) so that the 3 VMFS volumes appear in both vCenter server inventories. This is not a problem for me in itself as none of the VM’s on vCenter1 will ever use the datastores VMFS2 or VMFS3 and none of the VM’s on vCenter2 will use the datastore VMFS1.

 

However I am concerned that there may be performance, file locking or possible data corruption issues by even allowing two separately managed clusters to have ‘access’ to the same LUN’s/datastores concurrently regardless of being ‘used’ or not.

 

I have tried detaching the disk devices on the relevant hosts. e.g detach the device associated with LUN_0 on ESXi4/5/6, while this looks like it stops the hosts from accessing LUN_0 it does permanently flag the VMFS2 and VMFS3 datastores on vCenter2 in an error state as “(inaccessable)” which is not desirable. Also not sure if the detach is persistent across host reboots or may unintentionally get reattached.

 

So is it safe to just allow all 6 hosts to have all 3 datastores mounted? and could there be possible locking or performance issues resulting from this?

 

Cheers,

Steve.

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