[dm-devel] mechanism for multipath to pass information to hardware handler
Eddie Williams
Eddie.Williams at steeleye.com
Fri Jun 26 20:01:57 UTC 2009
The problem is easy to duplicate using sg_persist to register/reserve
paths to a Clariion array and then fail the active path. The "enable"
path will fail to become active when the HONOR RESERVATION flag is not
set. Given of course that you have a Clariion array handy...
One question I have asked EMC is in what situations would you NOT want
to set this bit?
I can test out any changes you make in my test rig and I can probably
get the folks in the EMC lab I work with to test it as well.
Eddie
On Fri, 2009-06-26 at 12:45 -0700, Chandra Seetharaman wrote:
> Yes, Mike Christie and I were aware of this and it was one of the issue
> we were trying to resolve before we pushed scsi_dh interface upstream.
> (It is little complicated as we need the parameters to be set per
> vendor-product tuple).
>
> The original code I ported to scsi_dh interface was from Ed Goggin(who
> was working for EMC then). IIRC, he was also aware of this issue.
>
> When we pushed scsi_dh interface, we did get few of the EMC folks (on
> Cc) to review/test the code and they did, and this issue was not seen as
> a problem.
>
> We wanted to get back to that issue sometime later, got busy with other
> things, and it disappeared from my list of things-to-do as the
> regression was not seen as an issue (till now :)... I will get back to
> it.
>
> chandra
>
> On Fri, 2009-06-26 at 14:10 -0500, James Bottomley wrote:
> > On Wed, 2009-06-24 at 13:14 -0400, Eddie Williams wrote:
> > > I notice in scsi_dh_emc.c that there is a comment:
> > >
> > > TODO: need some interface so we can set trespass values
> > >
> > > I don't see where any such interface has been developed or even any
> > > discussion on the different mailing lists to create such an interface.
> > > Did I miss something?
> > >
> > > As it stands now there is no way that I can see to have the emc hardware
> > > handler support the "honor trespass" feature short of recompiling the
> > > module forcing the flag to be set. This leaves a feature that worked in
> > > earlier versions of multipath not working now.
> >
> > OK so as I understand it that means that the line
> >
> > hardware handler "1 emc 0 1"
> >
> > now fails to function correctly because dm-emc no longer exists. That
> > makes this a functionality regression from 2.6.26 because of this
> > commit:
> >
> >
> > commit cb520223d7f22c5386aff27a5856a66e2c32aaac
> > Author: Chandra Seetharaman <sekharan at us.ibm.com>
> > Date: Thu May 1 14:50:34 2008 -0700
> >
> > [SCSI] scsi_dh: Remove hardware handlers from dm
> >
> > This patch removes the 3 hardware handlers that currently exist
> > under dm as the functionality is moved to SCSI layer in the earlier
> > patches.
> >
> > Because we haven't actually moved all the functionality.
> >
> > James
> >
> >
> >
>
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