Hi Teiva,

You need to load up SAN SSO. THis will be a full installation of BE on each server connected to your SAN, with your central backup server as the SAN backup server sharing it's tape library.
Load up the full version on each SAN-attached server, run the wizard on it, and it will detect the tape library (which also needs to be SAN-attached). This will then enable LAN-free backups. You can also target a disk presented elsewhere, but make sure that your jobs point to specific B2D folders in that case.
I would suggest doing this on servers with large amounts of data, so an Exchange server, SQL server, File & Print etc. This is due to the expense of having full versions installed.
Here is a link to the Backup Exec 12.5 Admin's Guide. It details how it gets installed:

http://support.veritas.com/docs/258734

I used this very successfully.

Ignore the SAN SSO idea if you are sharing SAN Storage between your ESX host on your media server purely for the purposes of backup. using AVVI.

The AVVI option should call the VCB Framewor/k Proxy which contains druiuvers to access and snap the ESX disk (that is correctly showing as 'Unknown Volume')

Your symptoms sound like Backup Exec is making the request to VCB and it that this request is timing out - if this is the case then the VCB Processes needs troubleshooting (possibly with VMWare's help) - although a proper support case with Symantec could assist as they have ways to enable extra logging that may show the problem.

 SSO is not the solution that I know of 100%.

This has to do with either the iSCSI SAN, or something I'm missing on the SAN setup along with the BE/VCB server config.

I'm going to try using an FC SAN, and also troubleshoot running vcbmounter.exe directly, and see what happens.  I believe BE is just calling that EXE anyways to do it's work.

Colin, yes I'm using AVVI.  Like I said, NBD works like a champ, SAN not so much.  WIth NBD I'm only getting about107MB/min or so, I need better throughput than that.

 Hmm - vaguely remember something about iSCSI not supporting the SAN VCB transport - if I am correct the information will be on VMWare's support site as it will be a VCB limitation.

EDIT: Looks like I might be wrong about this - although there are some comments on VmWare forums that some iSCSI implementations don't seem to work - however the basic guides for VCB from VMWare do say that SAN mode should work with iSCSI

 Had another thought are you presenting your  disk storage over fibre channel to the ESX server, but iSCSI to the VCB Proxy - as one of the requirements is that the same LUN should be presented to both ESX server and VCB Proxy which I suspect might be difficult to do if you have 2 different connection standards