setup Pathpriority manually

setup Pathpriority manually

[Markus]

Hi,

i do have an active-passive Storage where the LUN could be used by
both Controllers but one is bloody slow. I tried all
/sbin/mpath_prio_* ways do determin which is the "active" one but none
of them worked. Is there a way to set this manually? Is there a
different way to determin which is which rather than using the
existing Commands?

Thanks in advance
Markus

Re: setup Pathpriority manually

[Chandra Seetharaman]

On Thu, 2007-06-21 at 20:13 +0200, Markus wrote:
> Hi,
> 
> i do have an active-passive Storage where the LUN could be used by
> both Controllers but one is bloody slow. I tried all
> /sbin/mpath_prio_* ways do determin which is the "active" one but none
> of them worked. Is there a way to set this manually? Is there a
> different way to determin which is which rather than using the
> existing Commands?

If your device is not one of the supported devices, you can ask the
vendor about how to determine the active and passive paths.

mpath_prio_tpc is a good example of how the active/passive device
information is used to determine the path priority.
  
> 
> Thanks in advance
> Markus
> 
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
-- 

----------------------------------------------------------------------
    Chandra Seetharaman               | Be careful what you choose....
              - sekharan@us.ibm.com   |      .......you may get it.
----------------------------------------------------------------------

Re: setup Pathpriority manually

[Hannes Reinecke]

Chandra Seetharaman wrote:
> On Thu, 2007-06-21 at 20:13 +0200, Markus wrote:
>> Hi,
>>
>> i do have an active-passive Storage where the LUN could be used by
>> both Controllers but one is bloody slow. I tried all
>> /sbin/mpath_prio_* ways do determin which is the "active" one but none
>> of them worked. Is there a way to set this manually? Is there a
>> different way to determin which is which rather than using the
>> existing Commands?
> 
> If your device is not one of the supported devices, you can ask the
> vendor about how to determine the active and passive paths.
> 
> mpath_prio_tpc is a good example of how the active/passive device
> information is used to determine the path priority.
>   
Yes, but this assumes that documentation about the device is available.
That is not always the case (no NDA, uncooperative Vendors, or Vendor
gone out of Business etc.)

There is actually an easier way to do this: As all the mpath_* callouts
are in fact standalone programs, so you can easily supply your own callout.
Just write a small shell script which takes the device name as input.
The priority is just the return value of that program; the path with
the highest priority will take precedence over all the others.
Paths with identical priorities will be grouped into a path group if
the policy is set to 'group_by_prio' (which I would recommend if a
priority callout is specified).
The task of figuring out the physical location of a controller by
specifiying the device node is left to the reader.
But relying on udev here might be dangerous as multipathd might run
in parallel to udev.

HTH.

Just out of curiousity: Which machine is that?
Would be an idea to put that into the hardware table, if only with
a large fat
"Don't use that array unless you know what you're doing"
kinda-thing warning.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)

Re: setup Pathpriority manually

[Markus]

Hannes,

thanks for putting some light on that - i would highly appriciate if
you could give me a small sample script so that i could adopt? Also i
think it would be good to supply those samples along with
multipath-tool package for reference...
Your question regarding the array: I´am talking about an FalconStor
IPStor Virtualisation engine (like IBM SVC or Datacore) which sits
between the Client and it´s Storage.

Thanks in advance
Markus

2007/6/22, Hannes Reinecke <hare@suse.de>:
> Chandra Seetharaman wrote:
> > On Thu, 2007-06-21 at 20:13 +0200, Markus wrote:
> >> Hi,
> >>
> >> i do have an active-passive Storage where the LUN could be used by
> >> both Controllers but one is bloody slow. I tried all
> >> /sbin/mpath_prio_* ways do determin which is the "active" one but none
> >> of them worked. Is there a way to set this manually? Is there a
> >> different way to determin which is which rather than using the
> >> existing Commands?
> >
> > If your device is not one of the supported devices, you can ask the
> > vendor about how to determine the active and passive paths.
> >
> > mpath_prio_tpc is a good example of how the active/passive device
> > information is used to determine the path priority.
> >
> Yes, but this assumes that documentation about the device is available.
> That is not always the case (no NDA, uncooperative Vendors, or Vendor
> gone out of Business etc.)
>
> There is actually an easier way to do this: As all the mpath_* callouts
> are in fact standalone programs, so you can easily supply your own callout.
> Just write a small shell script which takes the device name as input.
> The priority is just the return value of that program; the path with
> the highest priority will take precedence over all the others.
> Paths with identical priorities will be grouped into a path group if
> the policy is set to 'group_by_prio' (which I would recommend if a
> priority callout is specified).
> The task of figuring out the physical location of a controller by
> specifiying the device node is left to the reader.
> But relying on udev here might be dangerous as multipathd might run
> in parallel to udev.
>
> HTH.
>
> Just out of curiousity: Which machine is that?
> Would be an idea to put that into the hardware table, if only with
> a large fat
> "Don't use that array unless you know what you're doing"
> kinda-thing warning.
>
> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke                   zSeries & Storage
> hare@suse.de                          +49 911 74053 688
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: Markus Rex, HRB 16746 (AG Nürnberg)
>