Presenting a volume LUN Globally or not?

[gjburg]

Hi, I can't find an answere to my question anywhere.

But I'm trying to find the advantage or disadvantage of presenting a SAN Volume Globally or to map it per Host WWN?

We've one volume presented per host and one presented globally. Now we have to expand with a new ESX server and a new volume.

Should I present the new volume also globally and then change/remove the old per host presented volume also to globally?

[Uwe Zessin]

What storage array are we talking about? I've never heard the term "Presenting a volume LUN Globally". And why is it "present/global" vs. "map/WWN" ?

If using an ESX farm it makes sense to present the volumes to all ESX servers so that one can use features like VMotion, storage VMotion, cold migration.

System or boot volumes are often presented to one server only unless we're dealing with single-image capable systems like OpenVMS or Tru64 Unix.

[gjburg]

Hi, it's a MSA2000 with 4 esx4 machines

The first Volume on the MSA that has been presented to the ESX machines is mapped per host.

The second volume has been presented "Globally"

So when we want to expand our situation can I use the Globbaly LUN option for a next volume.

[Uwe Zessin]

Ah, you are talking about the "Global Host List" on an MSA2000 Generation 1?

I would *NOT*, *NEVER* present *ANY* volumes through it!! Imagine what happens if you add a server with a different OS to the MSA? It will immediately have access to all ESX datastores and can trash them!!

[gjburg]

Ok I think there will be no other hosts connected but you've make a clear statement.

See also the screenshot of which global volume option is used.

I will move the files of the current volume to the new volumes, remove the current volume and present it per host instead of globally.

Thanks

[Patrick Terlisten]

Hello,

you should use in every case an explicit mapping of logical volumes to hosts. This will prevent you from data loss, if another host is connected to the MSA. This host will, as Uwe already said, see the logical volumes.

Regards,
Patrick

[gjburg]

Last weekend I created a new volume mapped per host. Moved all files from the wrong configured host (to be sure) and then remapped this volume also per host instead of globally.

Thank you all for your advise!