On Monday 24 September 2007 11:31:17 Jan-Frode Myklebust wrote:
> On 2007-09-24, Nuno Fernandes <[EMAIL PROTECTED]> wrote:
> > I disconnect the fibres that link FC Switch to DS4700 (to the active
> > controller). It should send SCSI commands through passive links to ask
> > the storage to failover the LUNs active controller. This isn't working.
>
> What I think is happening here is that you might have:
>
> '=' -- meaning active
> '~' -- meaning passive
>
>       HBA1 ============ DS4x00 controller A ====== LUNx
>       HBA1 ============ DS4x00 controller B ====== LUNy
>       HBA2 ~~~~~~~~~~~~ DS4x00 controller B ~~~~~~ LUNx
>       HBA2 ~~~~~~~~~~~~ DS4x00 controller A ~~~~~~ LUNy

I have 4 paths to each lun.

(a) HBA1 ====== DS4x00 controller A  ==== LUNx
(b) HBA1 ~~~~~~ DS4x00 controller B  ~~~~ LUNx
(c) HBA2 ====== DS4x00 controller A  ==== LUNx
(d) HBA2 ~~~~~~ DS4x00 controller B  ~~~~ LUNx

When i cut off paths (a) and (c) it should send though paths (b) and (d) 
commands to failover the active controler of the LUNx from controller A to 
controller B. It that moment both paths (b) and (d) would be active and data 
should be accessible.

It's the same thing as EMC Clariion Active/Passive controller.

Thanks
Nuno Fernandes

>
> So when you fail active path for controller A, the rdac driver
> wants to send a notification to controller B that it should
> fail over, but ooops, the path for controller B is also gone.
>
> What you seem to want is that it shouldn't fail over to
> controller B, but rather use the standby path to controller A
> (and B). And this is what I don't think is supported in the
> RDAC driver, at least not the engenio/lsi version.
>
> So, the correct configuration is:
>
>       HBA1 ============ DS4x00 controller A ===== LUNx
>       HBA1              DS4x00 controller A ~~~~~ LUNy
>       HBA2 ============ DS4x00 controller B ===== LUNy
>       HBA2              DS4x00 controller B ~~~~~ LUNx
>
> And when you fail the path from HBA1 you'll get:
>
>       HBA1      x       DS4x00 controller A ~~~~~ LUNx
>       HBA1      x       DS4x00 controller A ~~~~~ LUNy
>       HBA2 ============ DS4x00 controller B ===== LUNy
>       HBA2              DS4x00 controller B ===== LUNx
>
> And you'll get almost the same redundancy since you have
> the active/passive paths between controllers and LUNs,
> instead of between HBAs and controllers.
>
> Am I making sense ? :-)
>
>
>   -jf
>
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