Trouble configuring MPIO with multipath-tools

Trouble configuring MPIO with multipath-tools

[Dale.R.Fowle]

Hi all, I'm wondering if anyone can help un-confuse me. =-)

I've been through about every document I can find on the internet trying to
chase down exactly how I'm supposed to configure devices for MPIO. I
haven't seen the same answer twice. Everything is different.

The most formal documentation I found was here:
http://portal.suse.com/sdb/en/2005/04/sles_multipathing.html

I've also been out to the multipath-tools resource page:
http://christophe.varoqui.free.fr/

I really haven't gotten anything to work yet. =-)

I also saw another issue addressed from this e-mail discussion board that
said really all you need to do is uncomment some lines in
/etc/multipath.conf and comment out some other lines and you're good to go.

So, to clear things up with the device mapper piece of things. Is there any
requirement of the multipath command that these devices have to be
pre-built using dmsetup before multipath will recognize and built a path
under /dev/dm-*? If so,...how do you setup two paths to one device in your
target_file? What's confusing to me for setting up two devices in a
"linear" fashion would seem like it's creating a concatenation of two
separate devices instead of creating two paths to one device (i.e. "0
1028160 linear /dev/hda 0 1028160 3903762 linear /dev/hdb 0" from the
dmsetup manpage). The only other options are to set them up as stripe or
error devices.

I'm not sure where to go next with this. I can see my two paths at /dev/sda
and /dev/sdb. Whether I partition them or not, multipath won't pick
anything up and display it with 'multipath -v2 -d' or 'multipath -l'. What
I get from 'multipath -v2 -d' is an error like this:

#multipath -v2 -d
error calling out /bin/false
error calling out /bin/false
#

Also, does multipathd or the multipath command itself update
/etc/multipath.conf when multipath configures or recognizes a device,..or
is it all a manual process? I can't say I've ever seen a device addressed
like this before:
                                                                            
          3600601607cf30e00184589a37a31d911                                 
                                                                            
                                                                            
                                                                            

Coming from a Solaris background, I'm used seeing the WWNN and/or the WWPN.
=-) I'm pretty new to the Linux world, so I understand that I'll have to
get used to seeing things differently sometimes.

Anyways, I'd appreciate any help anyone can offer. FYI, I'm running SLES 9
with SP2, multipath-tools 0.4.4 is installed, and I'm using a pair of
Qlogic 2340 HBAs. The storage array controllers are configured as
active/active. The Qlogic failover parameter is disabled due to my previous
trials playing with mdadm's mpio features as well.


Thanks,
Dale


Dale Fowle
Seagate Technology
Colorado Springs, CO
719-388-5584

Re: Trouble configuring MPIO with multipath-tools

[Bernd Zeimetz]

Hi,

> Anyways, I'd appreciate any help anyone can offer. FYI, I'm running SLES 9
> with SP2, multipath-tools 0.4.4 is installed, and I'm using a pair of

from my own experience I can strongly suggest to update the multipath-tools to 
something >= 0.4.5. Read Christophe's page 
http://christophe.varoqui.free.fr/wiki/wakka.php?wiki=Home and/or the 
git-changelog and you know why... 

Bernd

Re: Trouble configuring MPIO with multipath-tools

[Christophe Varoqui]

On lun, 2005-10-31 at 11:20 -0700, Dale.R.Fowle@seagate.com wrote:
> Hi all, I'm wondering if anyone can help un-confuse me. =-)
> 
> I've been through about every document I can find on the internet trying to
> chase down exactly how I'm supposed to configure devices for MPIO. I
> haven't seen the same answer twice. Everything is different.
> 
> The most formal documentation I found was here:
> http://portal.suse.com/sdb/en/2005/04/sles_multipathing.html
> 
> I've also been out to the multipath-tools resource page:
> http://christophe.varoqui.free.fr/
> 
I bet you'll volonteer to make some really nice doc when you'll have a
good insight of Linux mp-tools. :/

> I really haven't gotten anything to work yet. =-)
> 
> I also saw another issue addressed from this e-mail discussion board that
> said really all you need to do is uncomment some lines in
> /etc/multipath.conf and comment out some other lines and you're good to go.
> 
Yes, it all boils down to that.

But for a safe start, you should be happy with no config file at all.
Safe defaults should apply, and you can tweak one param at a time from
there to see its effect.

> So, to clear things up with the device mapper piece of things. Is there any
> requirement of the multipath command that these devices have to be
> pre-built using dmsetup before multipath will recognize and built a path
> under /dev/dm-*?

No. dmsetup is not recquired for mpio operation.
As for /dev/dm-* : they are not recquired to exist at all.
The agreement is to use /dev/mapper/{alias,wwid} nodes.

>  If so,...how do you setup two paths to one device in your
> target_file?

No target_file. No manual assemble.

>  What's confusing to me for setting up two devices in a
> "linear" fashion would seem like it's creating a concatenation of two
> separate devices instead of creating two paths to one device (i.e. "0
> 1028160 linear /dev/hda 0 1028160 3903762 linear /dev/hdb 0" from the
> dmsetup manpage). The only other options are to set them up as stripe or
> error devices.
> 
linear, stripe, error, multipath, ... are target policies.
Concatenation is the *only* policy to chain multi-line tables.
Each line can have a different target policy.

multipath-tools use only 1-line tables. All paths of a multipath are
specified on this single line.

Users should not have to mess with this low-level stuff.

> I'm not sure where to go next with this. I can see my two paths at /dev/sda
> and /dev/sdb. Whether I partition them or not, multipath won't pick
> anything up and display it with 'multipath -v2 -d' or 'multipath -l'. What
> I get from 'multipath -v2 -d' is an error like this:
> 
> #multipath -v2 -d
> error calling out /bin/false
> error calling out /bin/false
> #
> 
multipath -d won't do anything (dry mode).
You need to comment out the /bin/false prioritizer in the config file.

> Also, does multipathd or the multipath command itself update
> /etc/multipath.conf when multipath configures or recognizes a device,..or
> is it all a manual process?

The tools never touch /etc/multipath.conf

>  I can't say I've ever seen a device addressed
> like this before:
>                                                                             
>           3600601607cf30e00184589a37a31d911                                 
>                                                                             
>                                                                             
> Coming from a Solaris background, I'm used seeing the WWNN and/or the WWPN.
> =-) I'm pretty new to the Linux world, so I understand that I'll have to
> get used to seeing things differently sometimes.
> 
This is the default naming before recent upstream version.
You'll find the nodes in /dev/mapper/

> Anyways, I'd appreciate any help anyone can offer. FYI, I'm running SLES 9
> with SP2, multipath-tools 0.4.4 is installed, and I'm using a pair of
> Qlogic 2340 HBAs. The storage array controllers are configured as
> active/active. The Qlogic failover parameter is disabled due to my previous
> trials playing with mdadm's mpio features as well.
> 
Good. Keep it that way.

Regards,
cvaroqui