Forum Discussion

SteveLaw's avatar
Level 5
9 years ago

Multipathing software required for ESX datastores SAN volumes?


I have a NBU VMWare proxy server, NB on Windows 2008, that has SAN visibility of the ESX datastores and has been happily backing up VMs to Data Domain for over a year. Recently an additional ESX farm was built and a SAN fabric change was made to grant the same NBU VMWare proxy visibility of the datastores hosted by these new ESX hosts. However I can't backup these new VMs  - I get the error "Error opening the snapshot disks using given transport mode: Status 23". 

I checked Disk Manager on the VM proxy media server and there's a whole load of disks present that show as offline with the message "The disk is offline because it has a redundant path with another device". I raised a call with our SAN team but they passed it back saying it was a problem with the multipathing on the Windows server. I thought this was odd as we've been using that server to backup VMs from the original ESX farm without a problem, so why would multipathing be an issue for these additional luns? 

I checked the server and Microsoft MPIO is installed but it doesn't appear to be managing any luns. On the mpio command line the commands mpclaim.exe -s -d (which is supposed to show the disks being managed by mpio) and mpclaim.exe -s (Queries connected enterprise storage and displays as vendor-product id strings) show mpio isn't doing anything:


So my question is (finally!): do you need multipathing drivers like Powerpath or MPIO for a Win2008 R2 Netbackup VMWare Proxy server to be able to read and backup from the ESX datastores? I don't appear to have any multipathing but it has been working on one ESX farm for a long time.








  • @Steve can tell you that I have used vmware backup with multipathing in Netbackup 7.5, without issues other than the SAN restore thing which had to do with the api rather than the number paths.

    Think you best bet of resolving this is together with your SAN, Windows & VM administrator

    Looking at the diskpart output the disks 35,59,83,107 could be the same LUN/datastore again assuming 4 paths through the SAN fabrics, and that disk 11 is from the old VM farm.

    Just checked on a server, the path to the "low" level disk drives is:

    Computer Management -> System Tools -> Device Manager -> Disk Drives


  • From these posts: is clear that the the document "DOCUMENTATION: Support for NetBackup 7.x in virtual environments", here:

    ...used to list that there were some restrictions around multi-pathing for NetBackup with some Linux OS.  However this document no longer carries any reference to this, and so would appear to imply that these restrictions are no longer valid (but probably one can only assume for the most recent versions of NetBackup - because it doesn't say when the restrictions were lifted).  I'm aware that similar restrictions used to once also exist for Windows based VMware backup hosts.  But when was that restriction lifted?  And for which version of NetBackup?


    And yet at the time of the postings, from the version of the doc at the time, it was clear that multi-pathing was supported for Windows based VMware backup hosts - but which versions?


    Do you see how your question is very difficult to answer because you are on v7.5.0.6 and so it's not easy to determine whether your version matrix can support multi-path.  Maybe it can, and so all you need to do is install a DSM and/or multi-path driver and you'll be ok.

    But I don't know this for sure.  Maybe it does, maybe it doesn't for your old version.

    Hence I was suggesting to dig back through the old VDDK release notes to see when the support was introduced by VMware.

    Remember, this isn't a NetBackup question per-se, it's a VMware "interop" question.

26 Replies