Hi Sridhar. Thanks for your reply: > > We are testing migrations from a cluster running Pacific to Reef. In > > pacific we needed to tweak osd_mclock_max_capacity_iops_hdd to have decent > > performances of ou cluster. > > It would be helpful to know the procedure you are employing for the > migration. For now we run some benchmarks on a fairly small dev/test cluster. It has been deployed using cephadm and updated with cephadm from Pacific to Reef. What we observed, is that with Pacific, tweaking osd_mclock_max_capacity_iops_hdd, we can go from arround 200MB/s of writes up to 600MB/s of writes, on balanced profile. But with Reef, changing osd_mclock_max_capacity_iops_hdd does not change a lot the performances of the cluster. (Or if it does, they are small enough so I did not see them). That been said, the performances of Reef "out of the box" are what we expect of our cluster (arround 600MB/s), while with Pacific we needed to tweak manually osd_mclock_max_capacity_iops_hdd to get the expected performances. So there is definitely a big improvement there. What made me think that this option was maybe not used anymore, during the deploy of Pacific, each OSD pushes its own osd_mclock_max_capacity_iops_hdd, but deploying Reef not. We did not see any values for the OSDs in the ceph config db. In conclusion, we could say, at least on our pre-update tests, that mClock seems to behave a lot better in Reef than in Pacific. Luis Domingues Proton AG On Monday, 8 January 2024 at 12:29, Sridhar Seshasayee <sseshasa@xxxxxxxxxx> wrote: > Hi Luis, > > > We are testing migrations from a cluster running Pacific to Reef. In > > pacific we needed to tweak osd_mclock_max_capacity_iops_hdd to have decent > > performances of ou cluster. > > > It would be helpful to know the procedure you are employing for the > migration. > > > But in reef it looks like changing the value of > > osd_mclock_max_capacity_iops_hdd does not impact cluster performances. Did > > osd_mclock_max_capacity_iops_hdd became useless? > > > "osd_mclock_max_capacity_iops_hdd" is still valid in Reef as long as it > accurately represents the capability of the underlying OSD device for the > intended workload. > > Between Pacific and Reef many improvements to the mClock feature have been > made. An important change relates to the automatic determination of cost > per I/O which is now tied to the sequential and random IOPS capability of > the underlying device of an OSD. As long as > "osd_mclock_max_capacity_iops_hdd" and > "osd_mclock_max_sequential_bandwidth_hdd" represent a fairly accurate > capability of the backing OSD device, the performance should be along > expected lines. Changing the "osd_mclock_max_capacity_iops_hdd" to a value > that is beyond the capability of the device will obviously not yield any > improvement. > > If the above parameters are representative of the capability of the backing > OSD device and you still see lower than expected performance, then it could > be some other issue that needs looking into. > -Sridhar > _______________________________________________ > 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
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