Re: EVMS Submission for 2.5

[Kevin Corry <corryk@us.ibm.com>]

On Wednesday 02 October 2002 18:02, Alexander Viro wrote:
> On Wed, 2 Oct 2002, Kevin Corry wrote:
> > So the question is, will there be a method to simply get a list of
> > registered disks on the system, or an API to call to run a function for
> > each disk? If so, we'll gladly switch to using that. If not, do you have
> > any suggestions for how this kind of functionality can be achieved with
> > your upcoming changes?
>
> That _really_ depends on the nature of functions you want to call that
> way.
>
> I might agree with something along the lines of
> 	* when evms is initialized, it's notified of all existing gendisks
> 	* whenever disk is added after evms initialization, we notify evms
> 	* whenever disk is removed, we notify evms

This sounds like it would be exactly what EVMS needs. The only thing we would 
want to add to this list is: "*whenever a disk is modified, notify evms". For 
example, with removable media drives (such as Zip and Jaz), when a cartidge 
is changed, the capacity of the drive might change, and we would like to be 
notified of that event.

> However, I doubt that it's what you really want.  In particular, you
> probably want to see partitioning changes as well as gendisk ones
> (and no, "evms will handle all partitioning" is _not_ an acceptable
> answer).

EVMS won't really be interested in partitioning changes. It only cares about 
whole devices, i.e. minor_shift == 0.

> Moreover, "gendisk is here" != "something is in the drive".

Will there be a common method for determining "media present"? The current 
method EVMS uses to determine "media changes" is somewhat inconsistent 
between IDE and SCSI.

> IOW, the real question is what are you going to do with that list of
> gendisks?

EVMS will try to read volume metadata from each device and activate volumes 
if it finds any pertinent metadata.

-- 
Kevin Corry
corryk@us.ibm.com
http://evms.sourceforge.net/