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Re: [dm-devel] multipath prio_callout broke from 5.2 to 5.3

This thread has been great information since I'm looking at the same type of thing. However it raises a couple of (slightly off-topic) questions for me. My recent upgrade to fedora 10 broke my prio_callout bash script just like you described, but my getuid_callout (a bash script that calls udevadm, grep, sed, and iscsi_id) runs just fine. Are the two callouts handled differently?

Also, is there an easy way to know what tools are in the private namespace already? My prio_callout script calls two other binaries: /sbin/udevadm and grep. If I go to C-code, handling grep's functions myself is no problem, but I'm not confident about re-implementing what udevadm does. Can I assume that since /sbin/udevadm is in /sbin that it will be available to call via exec()? Or would I be right back where we are with the bash scripting, as in having to include a dummy device as you described?

Finally, in my case I've got two redundant iscsi networks, one is 1GbE, and the other is 10GbE. In the past I've always had symetric paths, so I've used round-robin/multibus. But I want to focus traffic on the 10GbE path, so I was looking at using the prio callout. Is this even necessary? Or will round-robin/multibus take full advantage of both paths? I can see round-robin on that setup resulting in either around 11Gbps or 2 Gbps, depending on whether the slower link becomes a limiting factor. I'm just wondering if I am making things unnecessarily complex by trying to set priorities.

Thanks for all the help.


 Ty! Boyack
 NREL Unix Network Manager
 ty nrel colostate edu
 (970) 491-1186

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