Re: [Scst-devel] ALUA Active/Passive

[Bart V. A. <bar...@sa...>]

On 09/22/2015 03:01 PM, Aaron Knister wrote:
> My failover procedure goes like this:
>
> - Put all device group target groups into the transitioning state (echo
> transitionin > /sys/kernel/scst_target....)
> - On the master, replace the LUN mapped to the real device with the
> nullio device
>
> However, as soon as I perform the 2nd step the LUN beings responding to
> commands (despite it's state reporting as "transitioning") and writes to
> the LUN disappear into a black hole :(
>
> Is there a better way to do this?

Maybe I'm missing something, but do you really need the "transitioning" 
state ? If the ALUA state would e.g. be changed into "unavailable" that 
will cause SCST to reject all future write operations. And the LUN 
replacement action will only finish after any ongoing write operations 
have finished.

Please note that at least Windows initiator systems do not handle the 
"transitioning" ALUA state very well. It causes the MPIO driver to 
busy-wait until the ALUA state has been changed again into another state.

Bart.