Re: [dm-devel] user defined device name and table

[Pedro Bandim Faustino <pedro faustino fccn pt>]

Hi Ben,

They do change names, the thing is that when the drivers are first 
loaded at boot time, /dev/dm-0 gets multipathed and mapped to 
/dev/mpath/mpath0 and /dev/mapper/mpath0
Afterwards when there's a context switch to userspace, /dev/dm-2 gets 
multipathed and mapped to whatever alias I would have in multipath.conf 
(I could have blacklisted dm-2).

[root m07 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/dm-2             3.8G  1.8G  1.9G  48% /
/dev/dm-1              99M   24M   70M  26% /boot
/dev/sde1              92G  188M   87G   1% /log
tmpfs                1014M     0 1014M   0% /dev/shm


So what I did was first change the table (modifying the init script of 
the initrd), and booted.
Then I've issued a dmsetup rename and afterwards a mkinitrd. I've also 
edited the multipath.conf in order to blacklist by WWID the local SAS 
disk and the boot LUN, and also defined some policies for the FC SAN I'm 
using (IBM DS4700), and booted.

This is now what I have:

[root m07 ~]# multipath -ll
SRV07_BOOT () dm-0 IBM,1814      FAStT
[size=4.0G][features=0][hwhandler=0]
\_ round-robin 0 [prio=0][enabled]
\_ 2:0:0:0 sda 8:0   [active][ready]
\_ 3:0:0:0 sdc 8:32  [active][ready]
\_ round-robin 0 [prio=6][active]
\_ 2:0:1:0 sdb 8:16  [active][ready]
\_ 3:0:1:0 sdd 8:48  [active][ready]

[root m07 ~]# cat /etc/multipath.conf
defaults {
       udev_dir                /dev
       polling_interval        2
       selector                "round-robin 0"
       path_grouping_policy    multibus
       getuid_callout          "/sbin/scsi_id -g -u -s /block/%n"
       prio_callout            /bin/true
       path_checker            readsector0
       rr_min_io               100
       rr_weight               priorities
       failback                immediate
       no_path_retry           fail
       user_friendly_name      yes
}

blacklist {
       # Blacklist the local disk
       wwid 35000c500057cd8d3
       # Blacklist the root disk
       wwid 3600a0b8000295d64000009304742b4c8
       devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
       devnode "^hd[a-z]"
       devnode "^cciss!c[0-9]d[0-9]*"
}

devices {
       device {
               vendor                  "IBM"
               product                 "1814      FAStT"
               path_grouping_policy    group_by_serial
               path_checker            tur
               prio_callout            "/sbin/mpath_prio_tpc /dev/%n"
               no_path_retry           queue
       }
}


Pedro Bandim Faustino
email/sip: pedro faustino fccn pt
www.fccn.pt

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Benjamin Marzinski wrote:
> On Tue, Nov 27, 2007 at 09:31:51AM +0000, Pedro Bandim Faustino wrote:
>   
> > Stefan Bader wrote:
> >     
> > > You should be able to change the name by creating a multipaths section 
> > > like below
> > >
> > > multipaths {
> > >    multipath {
> > >        wwid "3600a0b8000295d64000009304742b4c8"
> > >        alias "SRV07_BOOT"
> > >    }
> > > }
> > >
> > > If that does not work as expected, you might have to say "no" to the 
> > > user friendly names option.
> > >       
> > Hi Stefan,
> > I've tried that, but what happens is that once the multipathd starts 
> > I'll have duplicate multipaths, the one at boot time and this one by 
> > multipathd, with different names.
> >
> >     
>
> If you add aliases to the multipaths section, like Stefan decribed, and
> then rerun multipath, do the devices change names to given aliases? They
> should.  Then, you should be able to remake the initrd, and reboot and
> just see the alias.  If you try this, and it doesn't work, let me know.
>
> -Ben
>

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