Re: [dm-devel] prio_callout

[Christophe Varoqui <christophe varoqui gmail com>]

On mar., 2012-11-13 at 17:02 +0000, Jason Butler wrote:
> All,
> 
> 
> I have a specific need to use my own path priorities – now you have
> removed the prio_callout from Redhat 6.2 – are there any other ways I
> can do this?
> 
> 
> Or do you have some instructions for defining custom path priorities?
> 
You can point multipathd to a custom shared library.
To develop one, the easiest path is 

- cloning the upsteam repo
- copy an existing prioritizer (ex. libmultipath/prioritizers/const.c)
- modify it to suit your needs
- add it to libmultipath/prioritizers/Makefile
- rebuild


Only the getprio function is called by multipathd, and its return code
is the weight of the path passed as argument. Not as easy as a script,
but close ... and you gain the memlocking of the shared lib at
multipathd startup.

You may also check if the weighedpath prioritizer implements what you
need.

Best regards,
christophe varoqui
http://www.opensvc.com