DanielVaknin
Enthusiast
Enthusiast

iSCSI and fibre from different ESXi hosts to the same datastores

Hi,

We have a centralized EMC Unity storage which exposes the datastores to our ESXi hosts via iSCSi.

We are moving towards replacing all our iSCSi network to FC.

In order for that to happen, we bought a couple of new ESXi hosts which will be connected to the same storage machine (EMC Unity) and will be presented with the same LUNs as the "old" ESXi hosts.

Basically, the same LUNs are going to be exposed to the ESXi hosts via both iSCSi and FC.

My question is, if we currently have a few datastores with running VMs on them exposed via iSCSi, will I see the same datastores on the new ESXi hosts via FC (again, this is the same LUN we are talking about, just the connectivity protocol is different)?

I'm asking this, because if I do see the same datastore, I can then just vMotion all the VMs to the new hosts, and then disconnect the "old" ESXi hosts and "destroy" the iSCSi network (after all datastores and VMs will migrate to the new hosts . Is that true?

Thanks!

7 Replies
a_p_
Leadership
Leadership

A few years back, I asked EMC the same question for a VNX, and the answer was "Don't do this!". From what I was told, accessing the same LUN through different protocols (e.g. FC, and iSCSI) at the same time is not supported.

Maybe things changed for Unity, but I strongly suggest that you open a support case with EMC, and ask them to get an official answer.

André

DanielVaknin
Enthusiast
Enthusiast

Thanks for the fast reply!

I'll try to ask EMC regarding this.

In the meantime, does anyone have a more recent answer? or tried this configuration?

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kastlr
Expert
Expert

Hi,

as per following VMware article your approach isn't supported by VMware.

Accessing the same storage through different transport protocols, such as iSCSI and Fibre Channel is...

So it's not an EMC limitation, it's a VMware limitation.

Regards,

Ralf



Hope this helps a bit.
Greetings from Germany. (CET)
DanielVaknin
Enthusiast
Enthusiast

Thanks for this KB.

But I didn't fully understand if they talk about the same situation we have.

In the KB, they wrote "The same LUN cannot be presented to an ESXi host or multiple hosts through different

storage protocols. To access the same LUN, the hosts must always use a single protocol,

for example, either Fibre Channel only or iSCSI only."

I can understand why connecting a LUN to the same ESXi host through multiple storage protocols is not supported,

but we are not going to connect the LUN to the same ESXi hosts through different storage protocols.

Each ESXi host will "see" the LUN through a single protocol - iSCSI or FC.

Is that not supported as well?

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VMmao
Contributor
Contributor

Hi DanielVaknin,

we are in the same situation, did you have any answer from VMware or EMC? Is it supported?

Thanks

Maurizio

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DanielVaknin
Enthusiast
Enthusiast

Hi VMmao,

This is the response I got from VMware:

"Yes, you can setup as you expected for migration purpose. That KB is correct as it is only for one ESXi host i.e; you can not expose one lun to one host using 2 protocols. However, in your case the FC hosts are different from existing iSCSI hosts. Just make sure you do not use this setup in production environment.

Also, I would like to inform that you may not get the "as expected" performance from the hosts. But, you can vMotion the VMs off the existing hosts to the new DC hosts. "

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VMmao
Contributor
Contributor

Great, thank you very much!

Bye

Maurizio

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