Re: Do we need to implement sr START/STOP management

[Robert Hancock <hancockrwd@gmail.com>]

On 11/01/2011 12:35 AM, JiSheng Zhang wrote:
> Hi James,
>
> 2011/11/1 James Bottomley<James.Bottomley@hansenpartnership.com>:
>> On Tue, 2011-11-01 at 13:31 +0800, JiSheng Zhang wrote:
>>> Currently, there's no start/stop management in scsi cdrom driver to
>>> spin up/down the motor do we need to implement it?
>>
>> Say more ... like what you think it buys.  The auto spin down of a CD
>> tends to be the best power control we have and it's not even clear that
>> manufacturers have implemented any other useful power states.
>
> Does it mean the behavior depends on manufacturers? Some cd will spin
> down automatically? Even so, how about during shutdown just after reading
> something from cdrom?
>
> Thanks,
> Jisheng

I believe the main reason disks are stopped during shutdown is that for 
many hard drives that use head unloading, it's much better for the 
lifespan of the drive to do a powered head unload on software command 
before powering off than an emergency unload caused by a loss of power. 
I don't believe that optical drives have such an issue.