Help needed with RDAC in production environment!!

Help needed with RDAC in production environment!!

[S. J. van Harmelen]

Hi all,

Please look at the output from "multipath -ll"

backup (360019b9000d7e1100000444b46be82c4) dm-1 DELL    ,MD3000        
[size=200G][features=0][hwhandler=1 rdac]
\_ round-robin 0 [prio=3][active]
 \_ 1:0:1:2 sdh 8:112 [active][ready]
\_ round-robin 0 [prio=0][enabled]
 \_ 1:0:0:2 sdd 8:48  [active][ghost]
xen (360019b9000d7e1100000445a47314b36) dm-0 DELL    ,MD3000        
[size=200G][features=0][hwhandler=1 rdac]
\_ round-robin 0 [prio=3][enabled]
 \_ 1:0:0:3 sde 8:64  [active][ready]
\_ round-robin 0 [prio=0][enabled]
 \_ 1:0:1:3 sdi 8:128 [active][ghost]
vmware (360019b9000d7e1100000444846be81b6) dm-3 DELL    ,MD3000        
[size=200G][features=0][hwhandler=1 rdac]
\_ round-robin 0 [prio=3][enabled]
 \_ 1:0:0:0 sdb 8:16  [active][ready]
\_ round-robin 0 [prio=0][enabled]
 \_ 1:0:1:0 sdf 8:80  [active][ghost]
data (360019b9000d7ddab0000493846be81e5) dm-2 DELL    ,MD3000        
[size=200G][features=0][hwhandler=1 rdac]
\_ round-robin 0 [prio=3][active]
 \_ 1:0:1:1 sdg 8:96  [active][ready]
\_ round-robin 0 [prio=0][enabled]
 \_ 1:0:0:1 sdc 8:32  [active][ghost]

See the xen and vmware disks. They both display enable / enable instead
of active / enable. Is this correct? Or is a disaster waiting to happen?

Please advice!

Sander

Re: Help needed with RDAC in production environment!!

[Tore Anderson]

* S. J. van Harmelen

> See the xen and vmware disks. They both display enable / enable instead
> of active / enable. Is this correct? Or is a disaster waiting to happen?

If I understand correctly, "enabled" means something like "ready to use,
but not in active use".  The preferred PG will become active ("in active
use") once you send some I/O there.  Try "dd if=/dev/mapper/wmware
of=/dev/null count=10" or something like that, see if they go active then.

The semantics had me confused for a while too.  :-)

Regards
-- 
Tore Anderson

Re: Help needed with RDAC in production environment!!

[S. J. van Harmelen]

Thanks for the explanation. I had some troubles before, so I was afraid
that there was a problem with multipath/RDAC. Fortunately it turned out
to be something else...

And indeed, when sending some I/O only one of the paths became active :)

Sander


On Thu, 2007-11-15 at 08:33 +0100, Tore Anderson wrote:
> * S. J. van Harmelen
> 
> > See the xen and vmware disks. They both display enable / enable instead
> > of active / enable. Is this correct? Or is a disaster waiting to happen?
> 
> If I understand correctly, "enabled" means something like "ready to use,
> but not in active use".  The preferred PG will become active ("in active
> use") once you send some I/O there.  Try "dd if=/dev/mapper/wmware
> of=/dev/null count=10" or something like that, see if they go active then.
> 
> The semantics had me confused for a while too.  :-)
> 
> Regards