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Thursday, February 21, 2013

Direct SAN connection for Veeam - Connecting your VMFS disks to your Windows Server

This has been written about a hundred times or so, but I'm writing it here so it can be found all in one spot (for me as well as my readers). I had to go all over the web to gather bits and pieces of this information.

My Veeam server (running Windows 2008 R2) has a fiber connection (though this same principal applies to iSCSI). One of the scariest things I have ever done in my nine years of IT has been to let this Windows server "see" my production VMFS volumes. When I say "see" what I mean is that in the Windows disk management console, your VMFS volumes will be listed, but will be offline and not mounted in Windows with a drive letter.

BEFORE you give your server access to your VMFS volumes on the SAN side through an access control list of some sort, you need to prep your Windows server first. I have read that Veeam does this automatically on installation, but I'd rather do it myself and know absolutely that it's done. From everything I've read, if Windows initializes a VMFS volume and assigns it a drive letter, then that VMFS volume is hosed (shudder). Even worse, you're probably just installing Veeam, so you don't even have the best virtual machine backup software protecting you yet!

On your Windows box, you should do the following:
1. Open a command prompt (run as administrator)
2. Type this command and press enter: diskpart
   This opens the diskpart shell

3. Type this command and press enter: san
   This returns the current SAN policy. The SAN policy is what tells the system to automatically bring new media online or offline. What you want to see is "Offline All". If you see "Online All", simply enter the following to change it: san Policy=OfflineAll
    Type the SAN command again to ensure it's set the way you need it.

4. Type this command and press enter: automount
    This returns the current automount policy. You want to see the automatic mounting of new volumes DISABLED!!!!!! If yours returns enabled, run the following command: automount disable

5. Reboot your system so the changes take effect.

After rebooting, it pays to check the policies again. Half a minute now could save you a lot of explaining and hours of restoring from backups later. If you need help from within diskpart, or just want to read more about the syntax, type help within the shell. It also works for commands, like so: help san.


  1. Thanks for the synopsis. I just ran into this while trying to setup a physical server direct san access POC for Veeam. Problem I had was "SAN1" had all the vmfs volumes, and "SAN2" was being repurposed for creating NTFS volumes for the physical windows server to use for backup storage space. I installed Veeam first (because of the scary factor you mentioned) before attaching the physical host to either SAN. Then when I went to initialize and mount LUNs from "SAN2" as NTFS volumes, I was getting errors indicated the disk structure was corrupt and unreadable. As I understand it, my error was due to both of the diskpart settings that you mentioned and is a result of the protective measures taken to not ruin VMFS volumes by presenting them to a windows box. I'm still working on the correct order of operations for setting the direct SAN access model up when you are also using SAN volumes for NTFS storage on the Veeam server.

  2. If you could post your end procedure, that's be great! I KIND OF wish I had the problem of dealing with two SANs..... :)

  3. So I've just setup my Veeam B&R to use direct SAN to my 3PAR Storeserv 7200. Got the disks showing up in management as offline, etc. My Veeam is currently set for Automatic selection of proxy in the job, and auto settings across the board in the backup infrastructure setting for the "this server" proxy. My processing rate from a full backup job (6.2TB, deduped to 2.0TB, target is local array) is 339MB/s. Looks pretty good... but my processing rate BEFORE I had a 10GB DAC cable coming directly from my server into the 3PAR was 268MB/s. Since I've only got 3 jobs done TOTAL so far (one full a week - the incrementals show varying processing rate) I'm entirely unsure if Veeam is really using direct access.

    Is there ANY way to look at a complete job and see which proxy it used, and how it used it? The reason I ask is because I also have a Veeam proxy that is a VM, which I want it to bypass unless something happens to the DirectSAN setup.

  4. If you click "Statistics" on the job, and then click on one of the VMs, it will show you on the right side which proxy it used. Version 6 used to show what type of backups it was (Direct SAN connection or whatever), but I'm not seeing that anywhere. I never had to look, I only have one of everything and I KNOW it's running to fast to be the "network" style backup. You would have MUCH better luck postingin the Veeam Forums. That place is amazing. Seriously, I can't recommend that enough.

  5. Thanks Charles! I actually had just finished posting in the Veeam forum with this same question (because I've been impatient today with trying to figure this out.) I have looked at the statistics 20+ times... but never realized if I click on one of the VMs it shows me additional info! This was exactly what I needed... also if you were wondering... no its not using the directSAN :( Back to work!

  6. Good luck; glad I could be of some help!