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 :
a) does it serve any purpose to enter the minor devices (in my
case there's 4 of them) into rawdevices file? (Say, will this
tell Linux that in the event one path is down, it will take the
next available logical/minor device or will it help spread
the traffic load between the paths?)
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?
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?
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
"multipath -ll" output follows for one of the logical device :
mpath0 (360a9800056724439633449336c786d69)
[size=5 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [prio=8][enabled]
\_ 8:0:2:4 sdr 65:16 [active][ready]
\_ 8:0:3:4 sdx 65:112 [active][ready]
\_ round-robin 0 [prio=2][enabled]
\_ 8:0:0:4 sdf 8:80 [active][ready]
\_ 8:0:1:4 sdl 8:176 [active][ready]
Thanks a lot
U
On 5/20/08, Herta Van den Eynde <herta.vandeneynde@xxxxxxxxx> wrote:
>
> 2008/5/20 sunhux G <sunhux@xxxxxxxxx>:
> > Hi Hertha,
> >
> >
> > Thanks.
> > Noticed that in the rawdevices file, there's column for minor device
> > file name.
> >
> > I heard for each of the /dev/mpath/mpathx, there's actually
> > two corresponding
> > minor devices (/dev/sd...).
> >
> > Yes, 2 /dev/sdx devices are the actual physical path to the SAN while
> > /dev/mpath/mpathx is the logical path with redundancy (ie if one physical
> > path is down, it will use the other path).
> >
> > How do I find out the physical paths for a logical path?
> >
> >
> > Tks
> > U
>
> Depending on how the SAN is configured you may even have more that 2
> physical paths to a logical device.
> You should be able to see the mapping using the command 'multipath -ll'.
>
> Kind regards,
>
> Herta
>
> --
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> but it comes with a free ride around the Sun."
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