Pushing the multipath state info into the fabric

Pushing the multipath state info into the fabric

[Muneendra Kumar M]

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Hi ,

We are working on the SAN fabric side to collect and present the multipath status information to the SAN administrators.
So, I am looking forward to push the multipath state information to the fabric in the form of CT (Common Transport) frames, by using the libhba APIs.
Since the multipath daemon is already keeping track of the multipath device and state info, I feel that it is the correct place to add the code to push the info to the fabric.
Please kindly let me know your thoughts on this.


Regards,
Muneendra.

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Re: Pushing the multipath state info into the fabric

[Mike Snitzer]

On Thu, Oct 26 2017 at  6:18am -0400,
Muneendra Kumar M <mmandala@Brocade.com> wrote:

>    Hi ,
> 
> 
> 
>    We are working on the SAN fabric side to collect and present the multipath
>    status information to the SAN administrators.
> 
>    So, I am looking forward to push the multipath state information to the
>    fabric in the form of CT (Common Transport) frames, by using the libhba
>    APIs.
> 
>    Since the multipath daemon is already keeping track of the multipath
>    device and state info, I feel that it is the correct place to add the code
>    to push the info to the fabric.
> 
>    Please kindly let me know your thoughts on this.

Sounds like you'd probably want to expose APIs that enable you to access
the state you require from multipathd rather than train multipathd to
inject anything into the fabric.

But that is just my initial take.

Mike

Re: Pushing the multipath state info into the fabric

[Muneendra Kumar M]

Hi Mike,
Our intention is to train the multipathd for pushing the  multipath info into the fabric using LIBHBA api's.
Can we call libhba apis in multipathd to push the info into fabric?

Regards,
Muneendra.

-----Original Message-----
From: Mike Snitzer [mailto:snitzer@redhat.com] 
Sent: Thursday, October 26, 2017 8:06 PM
To: Muneendra Kumar M <mmandala@Brocade.com>
Cc: dm-devel@redhat.com
Subject: Re: Pushing the multipath state info into the fabric

On Thu, Oct 26 2017 at  6:18am -0400,
Muneendra Kumar M <mmandala@Brocade.com> wrote:

>    Hi ,
> 
> 
> 
>    We are working on the SAN fabric side to collect and present the multipath
>    status information to the SAN administrators.
> 
>    So, I am looking forward to push the multipath state information to the
>    fabric in the form of CT (Common Transport) frames, by using the libhba
>    APIs.
> 
>    Since the multipath daemon is already keeping track of the multipath
>    device and state info, I feel that it is the correct place to add the code
>    to push the info to the fabric.
> 
>    Please kindly let me know your thoughts on this.

Sounds like you'd probably want to expose APIs that enable you to access the state you require from multipathd rather than train multipathd to inject anything into the fabric.

But that is just my initial take.

Mike

Re: Pushing the multipath state info into the fabric

[Mike Snitzer]

(please don't top-post once someone establishes bottom-posting)

On Mon, Oct 30 2017 at 12:40am -0400,
Muneendra Kumar M <mmandala@Brocade.com> wrote:

> Hi Mike,
> Our intention is to train the multipathd for pushing the  multipath
> info into the fabric using LIBHBA api's. 
> Can we call libhba apis in multipathd to push the info into fabric?

I'll defer to others who maintain and develop multipathd but I'll say
that I think it'd be more logical/correct to _not_ code multipathd to do
this directly.  But rather have your own code that interfaces with
multipathd to get the multipath info and push it where you'd like.

Newer multipathd code that was added to make programmatic access to
multipathd state easier/possible includes:

1) multipathd show maps json
   multipathd show map $map json

2) Use libdmmp (see multipath-tools commit 4335abb36f33f1).  libdmmp
   provides access to the json output via C api.

(thanks to Todd and Gris for providing pointers to these interfaces)

Mike