On Mon, Aug 1, 2016 at 9:49 AM, Hannes Reinecke <<= a href=3D"mailto:hare@suse.de" target=3D"_blank">hare@suse.de> wrote:

On 07/31/2016 09:26 PM, Ch= ristophe Varoqui wrote:

Ben, Hannes,

Can you review this patch, adding a new 'serial' keyword to the
weightedpath prioritizer.

I compile-tested it only, as I have no testing environment at hand at
the moment.

I commited it in a separate 'weightedpath-serial' branch for now.
http://git.opensvc.com/?p=3Dmultipath-tools/.git;a=3Dcommitdiff;h= =3D4dd16d99281104fc3504ad73626894a5c3702fb3

Thanks,
Christophe Varoqui
OpenSVC

Well.
In general, sure, fine, I don't have any issues with that.
If the customer wants to diddle with his array that way...

The more general problem I'm seeing is that our current two-layered pri= ority setup (path groups with distinct priorities and paths within them) mi= ght not be leading to issues with larger and more complex scenarios.

ATM we already have the problem that clustered scenarios like this:

Storage node 1(active):
=C2=A0 Path 1 (optimal):
=C2=A0 =C2=A0 LUN 1, LUN2
=C2=A0 Path 2 (non-optimal):
=C2=A0 =C2=A0 LUN 1, LUN2

Storage node 2(passive):
=C2=A0 Path 1(optimal):
=C2=A0 =C2=A0 =C2=A0LUN 1, LUN2
=C2=A0 Path 2(non-optimal):
=C2=A0 =C2=A0 =C2=A0LUN 1, LUN2

can not be represented properly with multipath tools.
We are forced to either
a) set 'storage node 2' to 'failed', which would kill
=C2=A0 =C2=A0any cluster instance accessing only 'storage node 2' or
b) map all priorities from 'storage node 2' to '0',
=C2=A0 =C2=A0thereby losing all priority information

Things become even more convoluted if both storage nodes are in fact access= ible, or if someone would be using different transports.

Would something like "prio alua+weightedpath&quo= t; produce correct priorities for the path grouping ? where priorities repo= rted by alua would be added to those reported by weighted path. That syntax= extension would reduce the need to develop more complex prioritizers.

The prio_args to prio mapping, wouldn't be nice th= ough.

Concerning transports, we can also extend th= e weightedpath prioritizer, and if the multi-prioritizer setup is implement= ed we could even weight on serial+transport with a "prio weighedpath+w= eightedpath" setup.

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