bodnarg
3 Zinc

VMWare ESX 3.0 servers and VCM devices?

Can someone confirm if a VMWare ESX server should see LUN 0 (VCM device) for DMX and Symmetrix arrays?

I think this is correct with VCM enabled on the FA port as we have though we had a question from VMWare about trying to get that device cleared from our host.

I checked the VMWare connectivity guide and did a scan of Powerlink and was not able to find anything stating this was a problem or confirming that this should be visible.

Hoping someone can quickly confirm this.
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6 Replies
xe2sdc
5 Tungsten

Re: VMWare ESX 3.0 servers and VCM devices?

Flagging a device as "VCM" menas that this special device will be visible from every host zoned to an FA even if the device isn't explicitly masked. ESX does not NEED to see the VCM (since there is no Solution Enabler for ESX) and in old days the VCM device was usually write disabled. This may give some pain to ESX trying to "own" the device but being unable to write to it.

Since DMX3 the VCM is a GateKeeper and due to its small size the device is supposed to be ignored from ESX. Again with DMX3 you can use any given gatekeeper to manage VCM so you can even unmap the VCM from ESX FAs. With older boxes there was however a flag that rendered the VCM just like any other device (I.E. needs to be masked before being seen).

I think that you CAN hide the VCM from your ESX server :-) ..

BTW the VCM does not require to be at lun 0 .. it can be "relocated" elsewhere .. Or you can even choose to use lun-offset to hide the VCM to your ESX host.. :D

Message was edited by:
Stefano Del Corno
bodnarg
3 Zinc

Re: VMWare ESX 3.0 servers and VCM devices?

This has some very good information, but I guess my question still stands.

Is it a problem if VMWare sees the VCM device? I think you are saying it probably is not a major issue.

I think I am going to research how we could nicely hide the VCM device to avoid any confusion, but unfortunately VMWare is sharing an FA port with some other servers so I can not just disable this completely.

Bonus points if you know offhand how to hide the VCM device from just a single host on a given FA port :)
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xe2sdc
5 Tungsten

Re: VMWare ESX 3.0 servers and VCM devices?

You have options as I said ;-) .. But I first need to know what model of storage we are talking about :D .. Are you using a DMX3, a DMX 1/2 or a Symmetrix ??
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bodnarg
3 Zinc

Re: VMWare ESX 3.0 servers and VCM devices?

Yes on 2 of the 3 right now. Using storage from a DMX-1000 running 71 code and a Symmetrix 8830 running 68 code are both attached to this VMWare host.

These are shared FA ports so I have to be a little careful with how this is setup.

We are looking to possibly isolate the VMWare hosts on our new DMX-4 which is in the process of being installed/configured.

The only fix I can seem to come-up with would be to use LUN offset via the symmask command to put something at LUN 0. Not sure this is worth the effort or not since I do not think this is causing any real issue.
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xe2sdc
5 Tungsten

Re: VMWare ESX 3.0 servers and VCM devices?

VMWARE (as per emc71378) does not requires a lun at address 0.
If you want to hide the VCM we can work in that direction .. But however remember that ESX does not need LUN 0 :-)

In older Symmetrix (with codes up to 5671 AFAIK) you can ask your local friendly customer engineer to enable flag FF2_VCM_DV_Restricted on your boxes .. This means that PRIOR to enabling the flag you have to explicitly GRANT access to the VCM to the hosts that will still need to access the VCMDB becouse when enabling the flag, the device will become a volume just like any other and will require you to mask it before being able to see it.

With DMX3/4 (codes 5771 and later) the VCMDB is simply a gatekeeper so you can simply avoid mapping the VCMDB itself on the FA ports, resolving the issue at its root.
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korman
2 Bronze

Re: VMWare ESX 3.0 servers and VCM devices?

I am running ESX 3.5 and I do see the VCMDB at LUN ID 0 on all my ESX hosts down both vmba paths. I am running DMX-1000. I see the lun 0 on all my san hosts. The device is write-disabled and has not been an issue but is a bit anoying to look at.

Hope this helps
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