[TriLUG] Mutipathing under 2.6.x - udev/multipath/hotplug

[Aaron S. Joyner]

Greg Foster wrote:

>Hi Folks,
>
>Please excuse in advance if you've covered this already.  I'm setting
>up some fibre channel storage for MythTV, and want to achieve either
>'active/active' or active/passive' between the drives and the host.
>  
>
First, let me say, you're the first person I've ever heard of who's 
setting up FC-AL drives on Brocade switches for Myth TV...  :)  You have 
a serious TV addiction that might require professional help.

Secondly, I haven't dealt with FC-AL drives directly under Linux, so I 
can't offer any productive advice on the situation.  I've dealt with 
similar setups, but usually with other layers involved such as VMware 
ESX, or Solaris in similarly bare scenarios.  Having said that though, 
I'm very curious to hear what the end result of your investigations 
are.  Please share if you find the "best" or "most appropriate" way to 
access the drives to take care of the multipathing.

If it's any consolation, The setup I'm used to using with VMware ESX, 
Brocade switches, and IBM's TotalStorage (FAStT) disc controllers, we 
expose different LUNs with different preferred paths, in an 
active/passive setup.  I.e. some of the traffic is flowing across one of 
the paths, some on the other, and things can always fail over one way or 
the other, but it's not a truly active/active setup.  My understanding 
is this is a limitation of the controllers in the FAStT that don't allow 
active/active, but I could be wrong about that.  I suspect it may depend 
on what controllers you have in front of your discs.

Aaron S. Joyner