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Duncan Thomas wrote:
> We are working on some sort of distributed replacement for the locks in
> cinder, since file locks are limiting our ability to do HA. I'm afraid
> you're unlikely to get any traction until that work is done.
>
> I also have a concern that some backend do not handle load well, and so
> benefit from the current serialisation. It might be necessary to push
> this lock down into the driver and allow each driver to choose it's
> locking model for snapshots.

IMHO (and I know this isn't what everyone thinks) but I'd rather have 
cinder (and other projects) be like this from top gear ( 
https://www.youtube.com/watch?v=xnWKz7Cthkk ) where that toyota truck is 
virtually indestructible vs. trying to be a high-maintenance ferrari 
(when most openstack projects do a bad job of trying to be one). So, 
maybe for a time (and I may regret saying this) we could consider 
focusing on reliability, consistency, being the toyota vs. handling some 
arbitrary amount of load (trying to be a ferrari).

Also I'd expect/think operators would rather prefer a toyota at this 
stage of openstack :) Ok enough analogies, ha.

-Josh

>
> On 27 Jun 2015 06:18, "niuzhenguo" <niuzhenguo at huawei.com
> <mailto:niuzhenguo at huawei.com>> wrote:
>
>     Hi folks,____
>
>     __ __
>
>     Currently we use a lockfile to protect the create operations from
>     concurrent delete the source volume/snapshot, we use exclusive____
>
>     locks on both delete and create sides which will ensure that:____
>
>     __ __
>
>     __1.__If a create of VolA from snap/VolB is in progress, any delete
>     requests for snap/VolB will wait until the create is complete.____
>
>     __2.__If a delete of snap/VolA is in progress, any create from
>     snap/VolA will wait until snap/VolA delete is complte.____
>
>     __ __
>
>     but, the exclusive locks will also result in:____
>
>     __ __
>
>     __3.__If a create of VolA from snap/VolB is inprogress, any other
>     create requests from snap/VolB will wait until the create is
>     complete. ____
>
>     __ __
>
>     So the create operations from same volume/snapshot can not process
>     on parallel, please reference bp [1].____
>
>     I’d like to change the current filelock or introduce a new lock to
>     oslo.concurrency.____
>
>     __ __
>
>     Proposed change:____
>
>     Add exclusive(write) locks for delete operations and shared(read)
>     locks for create operations, to ensure that create from
>     volume/snapshot____
>
>     can work on parallel and protect create operations from concurrent
>     delete the source volume/snapshot.____
>
>     __ __
>
>     I’d like to get what’s your suggestions, thanks in advance.____
>
>     __ __
>
>     [1] https://blueprints.launchpad.net/cinder/+spec/enhance-locks____
>
>     __ __
>
>     __ __
>
>     -zhenguo____
>
>
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