Re: The PQ=1 saga

[Bart Van Assche <bvanassche@acm.org>]

On 1/27/23 11:57, Brian Bunker wrote:
> So the question becomes how should initial scan work when a LUN has a PQ=1 set.
> It is a valid, by spec with ALUA state unavailable but doesn’t seem to be
> handled. Why allow an sg device but not an sd one on initial scan in this case? There
> are probably many ways to fix this. I think the simplest is to allow sd device creation
> on LUNs were PQ=1, and only restrict PQ=3. I am not sure the side effect of this on other
> targets. The other approach which will no longer work after the revert is to trigger a
> rescan from the target. This is sub-optimal since it is disruptive. Any approach involving
> the ALUA device handler will not help since there is no device to transition if it is
> discovered with PQ=1.

When Mike Christie and I looked into the ALUA unavailable state many 
years ago we concluded that using this state is so troublesome that it's 
better not to use this state. How about using active/optimized and 
active/non-optimized instead?

Thanks,

Bart.