Re: Questions about SATA hotplug in linux 2.6

[Jeff Garzik <jeff@garzik.org>]

Shane Huang wrote:
> 1. If users unplug one SATA HDD(no-root partition) or SATA ODD when
> the system is running, then plug it back to the same SATA port,
> Should the system and SATA HDD/ODD still work well?

Yes.

> 2. How about users plug the SATA HDD/ODD in a different SATA port?
> Should it still work?

Yes.

For all hotplug-aware libata drivers, you should be able to unplug a 
SATA device _while_ it is actively reading or writing data, with no ill 
effects to the kernel.

You might lose cached and in-flight data of course, and userspace 
applications may or may not handle the disappearance of their underlying 
filesystem with grace and aplomb :)

But device hotplug should be reliable from a kernel standpoint [assuming 
driver support].


> These questions come up when our QA test our SB700 SATA drivers,
> but I don't know the SATA hotplug support in linux 2.6.
> Is there any guy who can give some official confirmation? :-)

The main thing of note with regards to hotplug is that the associated 
device (/dev/sdb, /dev/scd0, etc.) may change between plug and unplug. 
For example, if you unplug a SATA HDD then plug it back in, the user 
might see /dev/sdb disappear, and /dev/sdd appear -- even if it is the 
exact same HDD, on the exact same port.

	Jeff