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



-----Original Message-----
From: redhat-list-bounces@xxxxxxxxxx [mailto:redhat-list-
bounces@xxxxxxxxxx] 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@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


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