Hi Hertha, How to find out minor device of a major device (for entry inrawdevices file)

[Gerrard Geldenhuis]

> -----Original Message-----
> From: redhat-list-bounces at redhat.com [mailto:redhat-list-
> bounces at redhat.com] On Behalf Of sunhux G
> Sent: 20 May 2008 11:05
> To: General Red Hat Linux discussion list
> Subject: Re: Hi Hertha,How to find out minor device of a major device
(for
> entry inrawdevices file)
> 
> Hi Hertha/anyone else,
> 
> 
> Thanks, there's actually four paths
> (as 2 SAN switches x 2 fibre cables = 4 possible paths).
> 
> 
> Just four more questions :
> 
> 
> b) I can use fdisk /dev/mpath/mpathx, select "p" (partition) to
>     find out the disk capacity of each of the logical mpathx
>     device.  However, "df -k /dev/mpath/mpathx"  will not show
>     the true capacity.  If I have more than 10 of those logical
>     devices, this is going to be tedious.  Is there a faster/shorter
>     way to find out the capacities?

My multipath output looks like this:
[root at server ~]# multipath -l
repdb_or_sup_failoverdb (350003ac0144e024a) dm-7 3PARdata,VV
[size=500G][features=0][hwhandler=0]
\_ round-robin 0 [prio=0][active]
 \_ 0:0:0:1 sda 8:0   [active][undef]
 \_ 1:0:0:1 sdb 8:16  [active][undef]

which does show size. Don't know whether this data is available for all
types of sans but worth while testing. You can use grep and friends to
easily extract data.


> 
> c) if one of the four paths is broken for some reason, I suppose
>     that's when "multipath -ll" will show one path less.  How
>     can I find out which path needs replacement/fixing when
>     this happens?

multipath will show one of the paths as inactive. Its been a while since
I looked at our san stuff so I am typing from memory. As for determining
which path is broken I would be interested in the answer too as I cant
find it in my notes and I di think it was in there.

> 
> d) Last question is probably a SAN (Netapp) question :
>     how can I find out from Linux end, which physical disk in
>     the SAN is faulty

This will be specific to the type of san you are using and most likely
you would be using there specific tools to determine this.

Regards