Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

I'm working on a project which aims to make use of Ubuntu servers running on enterprise class hardware. In our case that means IBM HS23E blade servers, QLogic 4GB fibre channel extension cards and quite old IBM DS4500 disk array with two controllers. At the moment we have fibre channel as only boot option and Ubuntu Server 12.04 installed just fine and is able to boot without multipath. I'm not a linux professional myself but in our team we have people who will understand the technical stuff. Don't let my post confuse :)

The current situation is that we have only one fibre channel connection to a single disk array controller. Real life case would be of course quite different. At minimum we should have two fibre channel ports connected to two different switches and two different controllers.

However, we have no idea how to set up multipath tool. Is the DM-MPIO the right software? At minimum we should be able to boot when multiple connections are available and achieve fault tolerance when any of them should be down.

Since the disk array is not the latest hardware, I managed to find RDAC driver sources only for 2.6.x kernel. And we have 3.2.x. Another issue is to build a multipath.conf. The said driver sources are from IBM support and the QLogic drivers provided to Ubuntu installer are from Ubuntu site. It seems that RHEL and SLES would have near out of the box support but that is not an option for our project.

Actual questions: - What is the recommended software tool for multipath for Ubuntu Server 12.04? - Is there available pre-made configurations or templates? Does it require disk array / controller specific settings or do a more generic config work? - Do you have expriences on similar setup and like to share the knowledge?

I'll provide you with any additional information you might require.

share|improve this question
add comment

1 Answer

multipath-tools is still the right thing in Ubuntu 12.04, though I'm not sure about how well multipathing your boot device will work.

The below config is a starter, there is some device-specific config (almost none of which is required, but you probably don't want the defaults). Any two devices with the same WWID will be grouped into a single mpath device; you probably want to explicitly name them with an alias, like I have below.

If you have issues getting RDAC going to determine state you could use readsector0 as a fall back, though that's the kind of thing you'll need to test with real hardware and possibly speak to your vendor about.

devices {
        device {
                vendor "DELL"
                product "MD32xxi"
                path_grouping_policy group_by_prio
                prio rdac
                polling_interval 5
                path-selector "round-robin 0"  
                path_checker rdac
                prio_callout "/sbin/mpath_prio_rdac /dev/%n"
                hardware_handler "1 rdac"
                failback immediate
        }
}

multipaths {
    multipath {
        wwid 36842b2b0004c340e000003fb4c8702e2
        alias "iscsi-data1"
    }
    multipath {
        wwid 36842b2b0004c2ace000004d74cf701d4
        alias "iscsi-data2"
    }
}
share|improve this answer
    
We did little experimenting with multipath. Ubuntu help recommends using DM-MPIO's internal database for settings. It found the correct looking device automatically. Is the manual configuration needed when using those? It took a bit time to test various configurations and understand what is going on with the tool. –  mlampi Nov 27 '12 at 11:08
    
Should Ubuntu to be able to boot from SAN as soon as the valid multipath.conf is in place and multipath-tools with multipath-tools-boot are installed? –  mlampi Nov 27 '12 at 13:35
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.