Re: Loud "pop" coming from hard drive on reboot

[Tejun Heo <htejun@gmail.com>]

Tejun Heo wrote:
> Alan Cox wrote:
>>> Not that simple.  Most disks don't spin up on SYNCHRONIZE_CACHE if 
>>> its cache is clean.  Sadly some disks actually spin up when it 
>>> receives spin down command while spun down to immediately spin down 
>>> again, so we would be fixing problem for some number of disks while 
>>> breaking others.  :-(
>>
>> Snoop the last command sent to the drive, that tells you if you can skip
>> the cache flush ?
> 
> Thought about that and querying power state before doing shutdown 
> sequence but things get somewhat ugly because shutdown sequence is 
> driven from sd->shutdown().  We'll have to snoop both sync and shutdown 
> commands and check whether the system is shutting down.  Also, I felt 
> very uneasy about faking successful completion to SYNCHRONIZE_CACHE.
> 
> I dunno.  It's already too late for 2.6.21.  I was hoping we could get 
> distros to update shutdown utilities in not-too-distant future but I 
> have no experience with that.  Is that just a wishful thinking?
> 

FWIW, the the following message describes the proposed solution.

http://thread.gmane.org/gmane.linux.scsi/30487/focus=17392

-- 
tejun