[openstack-dev] [cinder] LVM snapshot performance issue -- why isn't thin provisioning the default?

Chris Friesen chris.friesen at windriver.com
Fri Sep 18 17:31:58 UTC 2015


On 09/18/2015 11:01 AM, John Griffith wrote:
>
>
> On Fri, Sep 18, 2015 at 9:06 AM, Chris Friesen <chris.friesen at windriver.com
> <mailto:chris.friesen at windriver.com>> wrote:
>
>     On 09/18/2015 06:57 AM, Eric Harney wrote:
>
>         On 09/17/2015 06:06 PM, John Griffith wrote:
>
>
>             Having the "global conf" settings intermixed with the backend sections
>             caused a number of issues when we first started working on this.  That's
>             part of why we require the "self.configuration" usage all over in the
>             drivers.  Each driver instantiation is it's own independent entity.
>
>
>         Yes, each driver instantiation is independent, but that would still be
>         the case if these settings inherited values set in [DEFAULT] when they
>         aren't set in the backend section.
>
>
>     Agreed.  If I explicitly set something in the [DEFAULT] section, that should
>     carry through and apply to all the backends unless overridden in the
>     backend-specific section.


> Bottom line "yes", ideally in the case of drivers we would check global/default
> setting, and then override it if something was provided in the driver specific
> setting, or if the driver itself set a different default.  That seems like the
> right way to be doing it anyway.  I've looked at that a bit this morning, the
> issue is that currently we don't even pass any of those higher level conf
> settings in to the drivers init methods anywhere.  Need to figure out how to
> change that, then it should be a relatively simple fix.

Actually, I think it should be slightly different.  If I set a variable in the 
global/default section of the config file, then that should override any 
defaults in the code for a driver.

So the order of descending precedence would go:

1) setting specified in driver-specific section of config file
2) setting specified in global/default section of config file
3) setting specified in driver-specific code
4) setting specified in global/default code (not sure if this exists)


Chris



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