Re: Spinning down sata disk before poweroff

[Paul Goyette <paul%whooppee.com@localhost>]

On Fri, 17 Jun 2016, Anindya Mukherjee wrote:

> Hi,
>
> I'm running NetBSD 7.0.1_PATCH (GENERIC) amd64 on a Dell laptop. 
> Almost everything is working perfectly, except the fact that every 
> time I shutdown using the -p switch, the hard drive makes a loud click 
> sound as the system powers off. I checked the SMART status (atactl and 
> smartctl) and after every poweroff the Power_Off-Retract-Count 
> parameter increases by 1.
>
> I did some searching on the web and came across PR #21531 where this 
> issue was discussed from 2003-2008 and finally a patch was committed 
> which resolved the issue by sending the STANDBY_IMMEDIATE command to 
> the disk before powering off. Since then the code has been refactored, 
> but it is present in src/sys/dev/ata/wd.c line 1970 (wd_shutdown) 
> which calls line 1848 (wd_standby). This seemed strange since the disk 
> was definitely not being spun down.
>
> I attached a remote gdb instance and stepped through the code during 
> shutdown, breaking on wd_flushcache() which is always called. The code 
> path taken is wdclose()->wdlastclose() (lines 1029, 1014). I can see 
> that the cache is flushed but then the device is deleted in line 1023. 
> Subsequently, power is cut off during shutdown, causing an emergency 
> retract. So, it seems at least for newer sata disks the spindown code 
> is not being called. I'm fairly new to NetBSD code so there is a 
> chance I read this wrong, so feel free to correct me.

Well, I'm definitely not an expert on the disk drivers, so your analysis 
is likely as good as any I could give!


> Ideally I'd like the disk to spin down during poweroff (-p) and halt 
> (-h), perhaps settable using a sysctl, but not during a reboot (-r). I 
> am planning to patch wdlastclose() as an experiment to run the 
> spindown code to see if it stops the click. Is this a known issue, 
> worthy of a PR? I can file one. I can also volunteer a patch once I 
> have tested it on my laptop. Comments welcome!

I think that this would be the best possible behavior.  Please submit a 
PR to document this change-request.

Also, it's not clear at the moment if this is only for ATA disks, or if 
similar issues (with perhaps similar fixes) exist for other disks, ie 
scsi and usb/umass.



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