Re: Default IDENTIFY timeout is 5000ms which is too short for enterprise disks

[AlanCui4080 <me@alancui.cc>]

Hi,

Thank you for your really really detailed response. And i was surprised by your
reply, hopefully that doesn't cost your time too much.

On Thursday, 23 April 2026 19:15，you wrote：
> My best guess is that it is a HDD firmware bug where the drive sometimes
> hangs after a STANDBY + COMRESET + IDENTIFY. Or claims to be ready before
> it is actually ready.
> 
> It could of course also be a bug in e.g. ata_wait_ready(), and we are sending
> the IDENTIFY command too quickly after the COMRESET, but if that was the case,
> I think we would have seen way more bug reports from different vendors by now.
> 

That's the same as what i guessed, the drive's firmware didn't implement the ATA
correctly, they either ignored the command or just don't want to reply. The vendor
do really not instrest about specification, they do even break the APM and changed
the meaning of standard SMART value.

I'm not a native speaker so the actually question that i want to ask is that
will kernel do quirk for those drives so let it just don't fail to avoid costing
extra 5 seconds and producing annoying erros on console?

> > 
> > > So I think the question is, at this point, can you read from the drive?
> > > 
> > > E.g.:
> > > # dd if=/dev/sda of=/dev/null iflag=direct bs=4K count=1
> > 
> > I will be blocked out of the shell for 5 secs unless the IDENTIFY succeed.
> 
> But as soon as you get a shell after a system resume, the above command
> succeeds, right?

Yes, that's correct.

> 
> My suggestion is to look at the zpool code to see how long it waits to finds
> all devices after a system resume before it kicks devices off the RAID array.
> 
> My initial feeling is that if your device is ready after 5 seconds after a
> system resume, then the timeout value for zpool to kick off a device must be
> very low.

I do believe that's about zpool, i migrated it into btrfs RAID now, it works very
well. And if you want to know, the timeout of TXG to commit is 5000ms also.

Alan