VCB CX500 multipathing

[cgshamilton]

Hi,

I'd like to use an existing SAN-connected server we have as a VCB proxy server. That server already has a big LUN available that we use as a backup-to-disk LUN.

As the server is connected to a CX500 using two HBA's, with PowerPath multipathing software installed, I removed the Powerpath software and disable 3 out of 4 of the disks. So now only 1 active path to SAN is being used.

However, when I try to make a backup, I get the infamous error:

"\[2007-03-02 15:38:27.789 'vcbMounter' 2844 error] Error: Failed to open the disk: One LUN could not be opened"

The requirements for the VCB are a bit vague to me: I understand that the VCB proxy needs to "see" the VMFS luns, but does that mean that they (1) have to be in the same zones on the SAN switch, or (2) that they need to be part of the same storage group (which connects a server to a LUN) within the Navisphere software ? Cause of the latter is the case, I can only attach the VMFS luns the VCB proxy and not use it concurrently with the existing lun.

So can this LUN not be opened because it can't see it altogether (cause I do see that the backup starts - it even copies the nvram file and logs) or that the incorrect path has been disabled? And if the latter, how can I verify which one to use ?

Any help would be greatly appreciated.

[dblake15]

Do you see the LUN in Disk Management of the VCB proxy?? You need to also make sure that the LUN IDs are the same on the SAN side. I also do believe that they need to be in the same storage group as well.

[cgshamilton]

I figured out some more things myself :

The VMFS LUNs need to be added to the storage group for the VCB proxy

Just one more thing that is needed: the host LUN ID's must match. This is the tricky part I think, as the host LUN ID on my esx boxes is 15, where it is 3 on my backup proxy.

Anyone any idea how to make these identical (via Navisphere) ?

[dblake15 · Accepted solution]

I think you have to remove and then readd. I know on the CX 700 you can change them after they are created. I don;t think you can do that on the 500.

[cgshamilton]

do you mean remove them from the Storage Group and readd? I can't change them once they are connected to a certain host.

[cgshamilton]

ok, when I removed them from the storage group, and wanted to readd them, I saw that (well hidden) you can indeed change the host LUN IDs !!

So I'll now give it another try

[VTorque]

It is my understanding that the entire path the LUN is presented to the ESX server and the Backup server needs to be the same, not just the Host LUN ID..

[jjamieson]

And how do you do it? I can't find it.. the CX700 GUI is somewhat convoluted.

[jjamieson]

Okay so I guess with the CX700 (or at least, ours) there's no obvious way to change the host ID via the web/java console but you CAN do it by clicking the Host ID field to the right when you add a new LUN to the storage group.

This works for us because the way we have it set up now, each host has it's own storage group.

Anyways, what a PITA. It's not that this whole thing is necessarily a big problem it just needs to be documented better on VMware's part. I'm very disappointed by the terse, "we'll tell you how it works but not how to do anything" documents surrounding VCB. Give us some examples, guys!

Otherwise, VMware documentation has been sufficient.

[DC1]

Hello

I am also trying to set up VCB with a CX500.

I have the same "One LUN could not be opened" message.

When I run the Pre backup script for Brightstor Arcserve, the mount appears for a second in the explorer and then disappears. As you have noticed the documentation is scarce

Have you managed to get any further with this?