I came across an enterprise NVMe used for BlueFS DB whose performance dropped sharply after a few months of delivery (I won't mention the brand here but it was not among these 3: Intel, Samsung, Micron). It is clear that enabling bdev_enable_discard impacted performance, but this option also saved the platform after a few days of discard. IMHO the most important thing is to validate the behavior when there has been a write to the entire flash media. But this option has the merit of existing. it seems to me that the ideal would be not to have several options on bdev_*discard, and that this task should be asynchronous and with the (D)iscard instructions during a calmer period of activity (I do not see any impact if the instructions are lost during an OSD reboot) Le ven. 1 mars 2024 à 19:17, Igor Fedotov <igor.fedotov@xxxxxxxx> a écrit : > 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, jsterr@xxxxxxxxxxxx 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? > > _______________________________________________ > > ceph-users mailing list -- ceph-users@xxxxxxx > > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
 |