Re: [PATCH 1/1] : Spinning up disk is observed on standby paths until timeout, resulting in longer path restoration time.

[Matthew Wilcox <matthew@wil.cx>]

On Fri, Feb 20, 2009 at 10:03:15AM -0600, James Bottomley wrote:
> > The port isn't coming out of standby state.  We send it a TEST_UNIT_READY,
> > it replies with a 0x04/0x0b.  At that point, we currently decide to send
> > it a START_STOP and wait 100 seconds.  This is clearly a crappy decision
> > on our part, we should just bail.
> 
> So we should be bailing on manual intervention, TP standby and TP
> unavailable?  It looks like TP assymetric access transition is waitable.

I think that's correct (and I think my version of this patch makes that
clearer).

SPC 4r14 isn't clear on 'Asymmetric Access Transition' -- I can't tell
whether that state is entered on transition *to* active, or *from*
active, or both.

> It also looks like offline and notify (enable spinup) required are also
> not worth waiting for ... although the latter is a SAS power management
> state which it's not clear to me how to handle properly.

Offline is only applicable to M and V (Media Changer and Automation)
devices, neither of which should be attached to by sd.

I don't know what 'Enable Spinup' is for -- maybe Doug knows?  Sending a
START_STOP to the device might be exactly what they intend for us to do.
Under a 'First, Do No Harm' theory, perhaps we should leave well enough
alone and just add Standby and Unavailable?

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."