On 01/29/2016 06:50 PM, Benjamin Marzinski wrote:
On Fri, Jan 29, 2016 at 02:10:52PM +0000, Nalla, Ravikanth wrote:
Hi Mike, Hannes, Ben
This seems like a problem that has already been solved with path groups.
If the path(s) in your preferred path group are there, multipath will
>>> use them. If not, then it will use your less preferred path(s), and
>>> load balance across them > how ever you choose with the path_selectors.
I admit that we don't have a path prioritizer that does a good job of
>>> allowing users to manually pick a specific path to prefer. But it
seems
>>> to me that there is > >where we should be solving the issue.
Yes as mentioned , it appears that we will be able to achieve the same
>> result using the above multipath{...} configuration. However as you
>> mentioned I felt that it is not that user friendly in specify the path
>> to prefer. So when you mentioned about solving the problem there, could
>> you please clarify on what you had in mind and is there anything
specific
>> from our implementation that can be used there ?
There are two changes that I'm working on.
1. I'm adding an option for the alua prioritizer so that setting the
ALUA TPG Preferred Bit will cause the alau prioritizer to put that path
in a group by itself (with the highest priority). Currently if the
preferred bit is set for an active/optimized path, and there are other
active/optimized paths, they are all grouped together, and there is no
way to change that. So, for people with ALUA enabled hardware, they can
just enable the option, and set the Preferred Bit.
Hmm? I was under the distinct impression that it's exactly the other way
round; at least in my code I have this:
switch(aas) {
case AAS_OPTIMIZED:
rc = 50;
break;
case AAS_NON_OPTIMIZED:
rc = 10;
break;
case AAS_LBA_DEPENDENT:
rc = 5;
break;
case AAS_STANDBY:
rc = 1;
break;
default:
rc = 0;
}
if (priopath && aas != AAS_OPTIMIZED)
rc += 80;
ie any path with the 'prio' bit set will be getting a differen priority
than those without. Consequently they'll be grouped into different
priority groups.
I'd be surprised if your code is different, but what do I know ...
2. For people that need to be able to control the exact priority, I'm
redoing the weighted handler to allow better ways to specify the paths
in a presistent manner. It won't be as simple as the alua method, but
it will be actually usable, unlike it's current state.
That, however, is greatly appreciated :-)
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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