Re: [dm-devel] Designing a new prio_callout

[Hannes Reinecke <hare suse de>]

Ethan John wrote:
> Thanks for the heads-up about ALUA. We're looking into it.
> 
> What is the purpose of the custom mpio_prio_* applications that ship
> with open-iscsi if not to handle multipathing?
> 
It is. mpath_prio_* are the priority callouts for multipathing.
They determine the layout of the multipath map.
Theory is that mpath_prio_* will return the priority for a
given path in relation to the entire multipath layout.

If used with 'group_by_prio' all paths with the same
priority will be grouped into one multipath group, and
the group with the highest priority will become active.

When all paths in a group fail, the group with the next
highest priority will become active. Additionally some
failover command (as determined by the hardware handler)
may be send to the target.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare suse de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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