[dm-devel] [PATCH 0/4] path latency prio fixes

[Guan Junxiong]

On 2017/12/4 23:11, Martin Wilck wrote:
> On Mon, 2017-12-04 at 22:23 +0800, Guan Junxiong wrote:
>>> An open question is what multipathd should do wrt path grouping if
>>> it
>>> only has preliminary prio values, in particular with group_by_prio.
>> For the open question, in this situation, IMO  it's reasonable to
>> overwriting
>> the preliminary prio values if we let the user/admin know : "this is
>> an
>> asynchronous priority checkers and it has high priority to the other
>> synchronous
>> prioritizer.
> This is not what I meant. Once we have the final prio values, it's of
> course the right thing to overwrite anything preliminary. 
> 
> The "open question" arises at the time when we only have the
> preliminary values: We may group paths wrongly. Really bad example: we
> might be putting active and passive paths of a storage system into the
> same path group, causing endless trespassing... we should probably use
> "failover" policy if "group_by_prio" is selected but no reliable
> priorities are available.

Thanks for your clarification. Agreed.