Open Stack

Hey Tony,
   This has been a long running pain point/problem for some of the 
drivers in Cinder.
As a reviewer, I try and -1 drivers that talk directly to the database 
as I don't think
drivers *should* be doing that.   But, for some drivers, unfortunately, 
in order to
implement the features, they currently need to talk to the DB. :(  One 
of the new
features in Cinder, namely consistency groups, has a bug that basically 
requires
drivers to talk to the DB to fetch additional data.  There are plans to 
remedy this
problem in the M release of Cinder.   For other DB calls in drivers, 
it's a case by
case basis for removing the call, that's not entirely obvious how to do 
it at the
current time.   It's a topic that has come up now and again within the 
community,
and I for one, would like to see the DB calls removed as well. Feel free to
help contribute!  It's OpenSource after all. :)

Cheers,
Walt
> Openstack/Cinder has a wealth of storage drivers to talk to different
> storage subsystems, which is great for users of openstack.  However, it
> would be even greater if this same functionality could be leveraged
> outside of openstack/cinder.  So that other projects don't need to
> duplicate the same functionality when trying to talk to hardware.
>
>
> When looking at cinder and asking around[1] about how one could
> potentially do this I find out that is there is quite a bit of coupling
> with openstack, like:
>
> * The NFS driver is initialized with knowledge about whether any volumes
> exist in the database or not, and if not, can trigger certain behavior
> to set permissions, etc.  This means that something other than the
> cinder-volume service needs to mimic the right behavior if using this
> driver.
>
> * The LVM driver touches the database when creating a backup of a volume
> (many drivers do), and when managing a volume (importing an existing
> external LV to use as a Cinder volume).
>
> * A few drivers (GPFS, others?) touch the db when managing consistency
> groups.
>
> * EMC, Hitachi, and IBM NFS drivers touch the db when creating/deleting
> snapshots.
>
>
> Am I the only one that thinks this would be useful?  What ideas do
> people have for making the cinder drivers stand alone, so that everyone
> could benefit from this great body of work?
>
> Thanks,
> Tony
>
> [1] Special thanks to Eric Harney for the examples of coupling
>
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