[dm-devel] [PATCH RFC 0/3] multipath-tools: coalesce heterogenous paths by referencing method

[Guan Junxiong]

Hi Martin,

I sent an updated patch to support coalesce heterogenous paths by
inserting udev rules file as suggested by you in this original patch a
few days ago. I have tested this solution and it works on the sd/nvme
disk at least.

Here is the updated patch using udev solution:
[dm-devel] [PATCH] multipath-tools: support for coalescing heterogenous paths
https://www.redhat.com/archives/dm-devel/2017-August/msg00213.html

What do you think of the new patch?  Please let me know if it is convenient to you .

Best Wishes,
Guan Junxiong

On 2017/7/24 15:41, Guan Junxiong wrote:
> Hello Martin,
> Thanks for your comments. Please find my comments inline.
> 
> On 2017/7/21 18:21, Martin Wilck wrote:
>> Hello Guan,
>>
>> On Fri, 2017-07-21 at 13:07 +0800, Guan Junxiong wrote:
>>> This three patches support coalescing heterogenous paths by
>>> referencing
>>> another path identifier. This is useful in the scenario of migrating
>>> data
>>> for heterogenous arrays without interrupting uplayer transaction.
>>> ...
>> Anyway, I'm wondering if multipath configuration is the right place to
>> apply a "fake" configuration like this. Have you considered doing this
>> on the udev level? Udev has the advantage that udev immediately sees
>> added or modified rules files. So if you want to pretend temporarily
>> that sda is indeed the same disk as sdd, you could insert appropriate
>> temporary udev rules to do that. This would have the additional benefit
>> that not only multipathd sees the mangled WWID but also the rest of the
>> system (IOW, multipathd's view of the system would be consistent with
>> the world outside multipathd).
> 
> "udev level " solution is a good thing. Thanks.
> I still have a doubt whether a udev rules is enough to meet this fake configuration.
> IOW ,in addition to udev rules , do we still have to write a C program to fetch 
> sth . I will write a demo of this to see whether it has problems or not.
> 
> Regards,
> Guan Junxiong
> 
> 
>> Postponing a detailed technical patch review until these questions are
>> clarified.
>>
>> Regards,
>> Martin
>>