Disabling the write cache and the bluefs_buffered_io did not change anything. What we see is that larger disks seem to be the leader in therms of slowness (we have 70% 2TB, 20% 4TB and 10% 8TB SSDs in the cluster), but removing some of the 8TB disks and replace them with 2TB (because it's by far the majority and we have a lot of them) disks did also not change anything. Are there any other ideas I could try. Customer start to complain about the slower performance and our k8s team mentions problems with ETCD because the latency is too high. Would it be an option to recreate every OSD? Cheers Boris Am Di., 28. Feb. 2023 um 22:46 Uhr schrieb Boris Behrens <bb@xxxxxxxxx>: > Hi Josh, > thanks a lot for the breakdown and the links. > I disabled the write cache but it didn't change anything. Tomorrow I will > try to disable bluefs_buffered_io. > > It doesn't sound that I can mitigate the problem with more SSDs. > > > Am Di., 28. Feb. 2023 um 15:42 Uhr schrieb Josh Baergen < > jbaergen@xxxxxxxxxxxxxxxx>: > >> Hi Boris, >> >> OK, what I'm wondering is whether >> https://tracker.ceph.com/issues/58530 is involved. There are two >> aspects to that ticket: >> * A measurable increase in the number of bytes written to disk in >> Pacific as compared to Nautilus >> * The same, but for IOPS >> >> Per the current theory, both are due to the loss of rocksdb log >> recycling when using default recovery options in rocksdb 6.8; Octopus >> uses version 6.1.2, Pacific uses 6.8.1. >> >> 16.2.11 largely addressed the bytes-written amplification, but the >> IOPS amplification remains. In practice, whether this results in a >> write performance degradation depends on the speed of the underlying >> media and the workload, and thus the things I mention in the next >> paragraph may or may not be applicable to you. >> >> There's no known workaround or solution for this at this time. In some >> cases I've seen that disabling bluefs_buffered_io (which itself can >> cause IOPS amplification in some cases) can help; I think most folks >> do this by setting it in local conf and then restarting OSDs in order >> to gain the config change. Something else to consider is >> >> https://docs.ceph.com/en/quincy/start/hardware-recommendations/#write-caches >> , >> as sometimes disabling these write caches can improve the IOPS >> performance of SSDs. >> >> Josh >> >> On Tue, Feb 28, 2023 at 7:19 AM Boris Behrens <bb@xxxxxxxxx> wrote: >> > >> > Hi Josh, >> > we upgraded 15.2.17 -> 16.2.11 and we only use rbd workload. >> > >> > >> > >> > Am Di., 28. Feb. 2023 um 15:00 Uhr schrieb Josh Baergen < >> jbaergen@xxxxxxxxxxxxxxxx>: >> >> >> >> Hi Boris, >> >> >> >> Which version did you upgrade from and to, specifically? And what >> >> workload are you running (RBD, etc.)? >> >> >> >> Josh >> >> >> >> On Tue, Feb 28, 2023 at 6:51 AM Boris Behrens <bb@xxxxxxxxx> wrote: >> >> > >> >> > Hi, >> >> > today I did the first update from octopus to pacific, and it looks >> like the >> >> > avg apply latency went up from 1ms to 2ms. >> >> > >> >> > All 36 OSDs are 4TB SSDs and nothing else changed. >> >> > Someone knows if this is an issue, or am I just missing a config >> value? >> >> > >> >> > Cheers >> >> > Boris >> >> > _______________________________________________ >> >> > ceph-users mailing list -- ceph-users@xxxxxxx >> >> > To unsubscribe send an email to ceph-users-leave@xxxxxxx >> > >> > >> > >> > -- >> > Die Selbsthilfegruppe "UTF-8-Probleme" trifft sich diesmal abweichend >> im groüen Saal. >> > > > -- > Die Selbsthilfegruppe "UTF-8-Probleme" trifft sich diesmal abweichend im > groüen Saal. > -- Die Selbsthilfegruppe "UTF-8-Probleme" trifft sich diesmal abweichend im groüen Saal. _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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