GEOM for multipath? How?

From: Danny Howard (dannyman_at_toldme.com)
Date: 11/09/05

  • Next message: Danny Howard: "Re: GEOM for multipath? How?" 
    Date: Wed, 9 Nov 2005 13:25:34 -0800
To: freebsd-geom@freebsd.org, freebsd-hackers@freebsd.org

    Hello,

    Alas, my fancy Engenio dual-FC disk array is inaccessible to me for
    testing. :( But we are working on switching over to RHEL due to
    availability of FC multi-path redundancy drivers for RHEL but nada for
    FreeBSD.

    I was reading Linux' md man page, which sounds awfully similar to geom,
    and they have a provider called:

      MUTIPATH
           MULTIPATH is not really a RAID at all as there is only one real device
           in a MULTIPATH md array. However there are multiple access points
           (paths) to this device, and one of these paths might fail, so there
           are some similarities.

           A MULTIPATH array is composed of a number of logical different
           devices, often fibre channel interfaces, that all refer the the same
           real device. If one of these interfaces fails (e.g. due to cable prob-
           lems), the multipath driver to attempt to redirect requests to another
           interface.

    And I says to myself "AHA! Multipath should be easy to implement on
    FreeBSD as well, via geom." But I can't find an obvious way given
    existing geom utils to do this. And like I said, the box I'd use this
    on is inaccesible for now.

    Basically, I'd want a provider, that would see two disks, and if it
    could talk to one disk, it would, else it would talk to the other.

    Anyone here have a multipath capable hardware infrastructure who could
    test out some applicable geom config? Like I say a third time ... I
    have a nice Engenio 2882 FC sitting in a Datacenter, 3,000 miles away,
    that is connected to a system that is offline. I get to visit after
    Thanksgiving ... :/

    Thanks,
    -danny 

    -- 
http://dannyman.toldme.com/
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