From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christopher Weis Subject: Re: RE: dm-devel Digest, Vol 18, Issue 2 Date: Tue, 2 Aug 2005 16:49:08 -0500 Message-ID: References: <1123014429.20148.3.camel@zezette> Reply-To: Christopher Weis , device-mapper development Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0737662036==" Return-path: In-Reply-To: <1123014429.20148.3.camel@zezette> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids --===============0737662036== Content-Type: multipart/alternative; boundary="----=_Part_7289_3147098.1123019348799" ------=_Part_7289_3147098.1123019348799 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On 8/2/05, christophe varoqui wrote: >=20 > On mar, 2005-08-02 at 15:07 -0400, goggin, edward wrote: > > On Tue, 02 Aug 2005 09:37:14 -0500 > > "Christopher C. Weis" wrote > > > > > I have a multipath SAN environment with storage controllers that are > > > active/active. However, the controllers are not active/active at the > > > LUN-level without a performance penalty, meaning if two > > > servers want to > > > see the same LUN (as in a clustered filesystem environment), they bot= h > > > need to be using the same controller. I'm trying to figure > > > out a way to > > > statically "order" the paths so that I can copy a config to all of th= e > > > nodes using the CFS. > > > > > > >From what I've read, in a single-server environment with controllers > > > such as the ones I'm dealing with, the path_grouping_policy should be > > > set to "group_by_serial", which should work fine, but in a clustered > > > environment, I need to be sure that the path ordering is the same. > > > > > > Are there any path_selectors, other than round-robin, that might > > > accomplish this? Any other ideas? > > > > > > > One was is to configure each multipath to have two groups with one grou= p > > having a higher priority than the other based on whether the path=20 > accesses > > the fast path controller. The assignment of the highest priority path= =20 > group > > is non deterministic when using the "group_by_serial" path grouping=20 > policy. > > > > Seems like you want to use the "group_by_priority" path grouping policy= =20 > and > > create and get_priority executable which when invoked will return a 1= =20 > for > > fast path and 0 for slow path. See the code for mpath_prio_emc, the > > get_priority executable for the EMC CLARiiON array in > > multipath-tools/path_priority/pp_emc/pp_emc.c. > > > Yes, also note "group_by_priority" path grouping policy may be overkill > for the context. PG produced by "group_by_serial" can be sorted with an > adequate prioritizer too. >=20 >=20 >=20 Does this mean that "group_by_serial" utilizes a "default_prio_callout"=20 program/script as well, or is there another callout (or something totally= =20 different that I'm missing)? Thx. ~Chris ------=_Part_7289_3147098.1123019348799 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On 8/2/05, christophe varoqui <christophe.varoqui@free.fr> w= rote:
On mar, 2005-08-02 at 15:07 -0400, goggin, edward wrote:
> On Tue, 02= Aug 2005 09:37:14 -0500
> "Christopher C. Weis" <ccweis@gmail.com> wrote
>
>= ; > I have a multipath SAN environment with storage controllers that are
> > active/active.  However, the controllers are not ac= tive/active at the
> > LUN-level without a performance penalty, me= aning if two
> > servers want to
> > see the same LUN (as= in a clustered filesystem environment), they both
> > need to be using the same controller.  I'm trying t= o figure
> > out a way to
> > statically "order"= ; the paths so that I can copy a config to all of the
> > nodes us= ing the CFS.
> >
> > >From what I've read, in a single-server envi= ronment with controllers
> > such as the ones I'm dealing with, th= e path_grouping_policy should be
> > set to "group_by_serial&= quot;, which should work fine, but in a clustered
> > environment, I need to be sure that the path ordering is the = same.
> >
> > Are there any path_selectors, other than ro= und-robin, that might
> > accomplish this?  Any other id= eas?
> >
>
> One was is to configure each multipath to have tw= o groups with one group
> having a higher priority than the other bas= ed on whether the path accesses
> the fast path controller. &nbs= p;The assignment of the highest priority path group
> is non deterministic when using the "group_by_serial" pa= th grouping policy.
>
> Seems like you want to use the "gr= oup_by_priority" path grouping policy and
> create and get_prior= ity executable which when invoked will return a 1 for
> fast path and 0 for slow path.  See the code for mpath_p= rio_emc, the
> get_priority executable for the EMC CLARiiON array in<= br>> multipath-tools/path_priority/pp_emc/pp_emc.c.
>
Yes, also= note "group_by_priority" path grouping policy may be overkill
for the context. PG produced by "group_by_serial" can be sort= ed with an
adequate prioritizer too.



Does this mean that "group_by_serial" util= izes a "default_prio_callout" program/script as well, or is there another callout (or something totally different that I'm missing)?

Thx.

~Chris
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