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

Eric Harney eharney at redhat.com
Thu Sep 17 17:31:11 UTC 2015


On 09/17/2015 05:00 AM, Duncan Thomas wrote:
> On 16 September 2015 at 23:43, Eric Harney <eharney at redhat.com> wrote:
> 
>> Currently, at least some options set in [DEFAULT] don't apply to
>> per-driver sections, and require you to set them in the driver section
>> as well.
>>
> 
> This is extremely confusing behaviour. Do you have any examples? I'm not
> sure if we can fix it without breaking people's existing configs but I
> think it is worth trying. I'll add it to the list of things to talk about
> briefly in Tokyo.
> 

The most recent place this bit me was with iscsi_helper.

If cinder.conf has:

[DEFAULT]
iscsi_helper = lioadm
enabled_backends = lvm1

[lvm1]
volume_driver = ...LVMISCSIDriver
# no iscsi_helper setting


You end up with c-vol showing "iscsi_helper = lioadm", and
"lvm1.iscsi_helper = tgtadm", which is the default in the code, and not
the default in the configuration file.

I agree that this is confusing, I think it's also blatantly wrong.  I'm
not sure how to fix it, but I think it's some combination of your
suggestions above and possibly having to introduce new option names.



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