[dm-devel] [PATCH 4/9] multipath-tools: add NetApp E-Series NVMe to hardware table

[Martin Wilck]

Steve,

On Wed, 2022-05-18 at 20:24 +0000, Schremmer, Steven wrote:
> > From: Xose Vazquez Perez <xose.vazquez at gmail.com>
> > Cc: NetApp RDAC team <ng-eseries-upstream-maintainers at netapp.com>
> > Cc: Martin Wilck <mwilck at suse.com>
> > Cc: Benjamin Marzinski <bmarzins at redhat.com>
> > Cc: Christophe Varoqui <christophe.varoqui at opensvc.com>
> > Cc: DM-DEVEL ML <dm-devel at redhat.com>
> > Signed-off-by: Xose Vazquez Perez <xose.vazquez at gmail.com>
> > ---
> >  libmultipath/hwtable.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/libmultipath/hwtable.c b/libmultipath/hwtable.c
> > index 814e727a..61a5aa16 100644
> > --- a/libmultipath/hwtable.c
> > +++ b/libmultipath/hwtable.c
> > @@ -845,6 +845,15 @@ static struct hwentry default_hw[] = {
> >                 .pgpolicy      = MULTIBUS,
> >                 .no_path_retry = NO_PATH_RETRY_QUEUE,
> >         },
> > +       {
> > +               /* E-Series NVMe */
> > +               .vendor        = "NVME",
> > +               .product       = "NetApp E-Series",
> > +               .pgpolicy      = GROUP_BY_PRIO,
> > +               .prio_name     = PRIO_ANA,
> > +               .pgfailback    = -FAILBACK_IMMEDIATE,
> > +               .no_path_retry = 30,
> > +       },
> >         /*
> >          * NEC
> >          */
> > --
> > 2.36.1
> 
> Nak. NetApp E-Series only supports these settings in certain
> configurations, and we prefer to handle it via our installation
> documentation.
> 

I don't follow. What harm is done to Netapp if these settings are
included? People can still follow your documentation, the end result
will be the same... no?

AFAICS, the only setting above that would only be supported in certain
configurations is PRIO_ANA, without which GROUP_BY_PRIO doesn't make
much sense. If the array is configured not to support ANA, this
configuration would lead to error messages and PRIO_UNDEF for all
paths, and thus "imply" multibus topology. Not beautiful, but also no
big harm done, IMO. 

If it's that you're concerned about, please provide the set of defaults
you prefer for E-Series, or explictly state that you prefer to run with
the generic NVMe defaults (const prio, failover policy).

In general, if vendor-recommended settings are strongly dependent on
storage configuration, host-side software defaults must try to match
the storage array's defaults. We shoud do this for E-Series, too. If
ANA needs to be explicitly enabled on the array by the admin, we
shouldn't enable it by default; but otherwise, we should.

Martin