I played with this feature a while ago and recall it had visible negative impact on user operations due to the need to submit tons of discard operations - effectively each data overwrite operation triggers one or more discard operation submission to disk.

And I doubt this has been widely used if any.

Nevertheless recently we've got a PR to rework some aspects of thread management for this stuff, see https://github.com/ceph/ceph/pull/55469

The author claimed they needed this feature for their cluster so you might want to ask him about their user experience.


W.r.t documentation - actually there are just two options

- bdev_enable_discard - enables issuing discard to disk

- bdev_async_discard - instructs whether discard requests are issued synchronously (along with disk extents release) or asynchronously (using a background thread).

Thanks,

Igor

On 01/03/2024 13:06, jst...@proxforge.de wrote:
Is there any update on this? Did someone test the option and has performance values before and after?
Is there any good documentation regarding this option?
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