The MD3000i isn't compatible with Linux native MPIO. It surprises me it sees any paths at all.

If you check the MD3000i support matrix (here) you'll see on page 6: "Citrix XenServer Dell edition 5.0  Single-path support only,
no RAID controller failover".

For Linux there's the RDAC driver, but that driver is compatible only with Red Hat Enterprise Linux (check support matrix for exactly which versions as it doesn't support all of them) and SuSE linux. The drivers won't properly install/work under other linux distros (e.g. CentOS, openSuSE, Ubuntu, etc).

According to this thread over at the Citrix Forums it does work:

http://forums.citrix.com/thread.jspa?threadID=239514

Also, it seems odd that there would be this entry in the multipath.conf if it was unsupported:

devices {
        device {
                vendor "DELL"
                product "MD3000i"
                path_grouping_policy group_by_prio
                getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
                path_checker rdac
                prio_callout "/sbin/mpath_prio_rdac /dev/%n"
                hardware_handler "1 rdac"
                failback immediate
        }

Am I missing something here?

So you're accepting someone's (non-Dell I'd say) findings over the Dell documentation that says that it's not supported?

If DM-MPIO would work (actually do load balancing and failover in case of a failure), why would Dell not list it in the support matrix as an option?

Have you tested your setup by generating IO and then pulling a cable and see if failover occurs (on this array it can take more than a minute, so be patient)?

As we know docs are always 100% accurate and updated the minute anything changes :emotion-5: , but yes I see your point.

I have tested pulling a cable from the host which works fine. However pulling a cable from the array does not.

Also, I am seeing load balancing on the links to one controller, however I can not get any LUNs mapped to the second controller, they just switch over to the first controller.

Anyway, I've got an appointment on Monday with a Dell support engineer, so hopefully we can get to the bottom of this as I doubt I'm the only one with this issue.

Problem solved! :emotion-2:

An update to the latest controller firmware on the MD3000i did the trick. I now have 4 of 4 paths on Xenserver and failover/multipath is working properly. Not sure why this made a difference, I didn't make any other config changes and it just started working.

So, although unofficial Multipath with Xenserver 5.0 and the MD3000i works just fine.

Just because DM-MPIO sees the paths, have you been able to confirm it's really doing MPIO? And have you tested failover to see if that maybe works too?

Yes, I have deactivated iSCSI interfaces on both the server and the MD3000i and it fails over. Additionally I'm seeing load balanced iSCSI traffic on both of the interfaces on the server.