Re: [gentoo-user] multipath.conf : learning how to use

["J. Roeleveld" <joost@antarean.org>]

On woensdag 14 augustus 2019 10:14:31 CEST Stefan G. Weichinger wrote:
> Am 14.08.19 um 08:36 schrieb J. Roeleveld:
> > Stefan,
> > 
> > On maandag 29 juli 2019 21:28:50 CEST Stefan G. Weichinger wrote:
> >> At a customer I have to check through an older gentoo server.
> >> 
> >> The former admin is not available anymore and among other things I have
> >> to check how the SAN storage is attached.
> > 
> > If you ever encounter that admin, make sure you hide the body :)
> 
> I only learn day by day what a mess all that is ...

If there is no documentation, it is a mess by definition.

> >> I see two devices sdc and sdd that should come from the SAN.
> > 
> > Interesting, are these supposed to be the same?
> 
> No, I don't think so. But maybe you'r right. No sdd in fstab or in the
> mounts at all and ...

See next item, make sure you do NOT mount both at the same time.

> > what do you get back from:
> > 
> > # /usr/bin/sg_vpd --page=di /dev/sdc
> > # /usr/bin/sg_vpd --page=di /dev/sdd
> > (As suggested in the multipathd.conf file you listed above)
> 
> these 2 look similar to me:
> 
> samba ~ # /usr/bin/sg_vpd --page=di /dev/sdc
> Device Identification VPD page:
>   Addressed logical unit:
>     designator type: NAA,  code set: Binary
>       0x600c0ff0001e91b2c1bae25601000000

> samba ~ # /usr/bin/sg_vpd --page=di /dev/sdd
> Device Identification VPD page:
>   Addressed logical unit:
>     designator type: NAA,  code set: Binary
>       0x600c0ff0001e91b2c1bae25601000000

> 
> > If "sdc" and "sdd" are the same disk, the "Adressed logical unit" id
> > should be the same for both.
> 
> So we have 0x600c0ff0001e91b2c1bae25601000000 twice, right?

Yes, IOW, the same device/LUN/whatever.
Do NOT mount both at the same time EVER

> There's a /dev/sdb as well, commented in fstab with "9750-8i Raid6
> (4x3TB + 2x4TB)" but that seems another "branch" of devices:
> 
> # /usr/bin/sg_vpd --page=di /dev/sdb
> Device Identification VPD page:
>   Addressed logical unit:
>     designator type: NAA,  code set: Binary
>       0x600605b00d0ce810217ccffe19f851e8

Yes, this one is different.

I checked the above ID and it looks like it is already correctly configured.
Is " multipathd " actually running?

If it were running correctly, you would mount " /dev/mapper/.... " instead of 
" /dev/sdc " or " /dev/sdd ".

> In the first week of september I travel there and I have the job to
> reinstall that server using Debian Linux (yes, gentoo-users, I am
> getting OT here ;-)).

For something that doesn't get updated/managed often, Gentoo might not be the 
best choice, I agree.
I would prefer Centos for this one though, as there is far more info on 
multipath from Redhat.