Micah Green did you apply any tuning parameters also to RHEL apart from the solution provided. As I can see some nodes swapping still.
Regards Manish On Sat, Jul 29, 2023 at 5:52 PM manish khandelwal < manishkhandelwa...@gmail.com> wrote: > Thanks Micah Green. Got the same resolution from the RHEL team. Will apply > and share the results. > > Regards > Manish > > On Sat, Jul 29, 2023 at 5:16 PM Micah Green <mgree...@gmail.com> wrote: > >> We have been experiencing swap issues on rhel 8.7.4 across 1000s of >> nodes. https://access.redhat.com/solutions/6785021. This is obtrusive >> enough that our linux engineering team decided to push a patch through to >> all of our teams. Once we updated the appropriate setting per the link I >> shared, all swap issues went away. >> >> On Thu, Jul 27, 2023 at 5:33 AM manish khandelwal < >> manishkhandelwa...@gmail.com> wrote: >> >>> Thanks Tibor. I know that swapping should be disabled, that is a general >>> recommendation. >>> I wanted to know i*f anyone using Cassandra on RHEL faced any issue >>> while moving from Rhel 7.x to Rhel 8.x. * >>> >>> Regards >>> Manish >>> >>> On Thu, Jul 27, 2023 at 2:29 PM Tibor Répási <tibor.rep...@anzix.org> >>> wrote: >>> >>>> That doesn’t sound like a RHEL issue. Swapping can severely impact >>>> performance, that’s why it is recommended to turn off swap on Cassandra >>>> nodes. This was recommended in the Cassandra documentation by DataStax[1]. >>>> Apache Cassandra is testing that and log a warning on startup [2] if >>>> swap is found enabled. >>>> >>>> Alternatively, the kernel behaviour can be tuned by setting the IO cost >>>> of swapping [3] that best fit your use-case. For a Cassandra node >>>> having sufficient physical memory this might end up at zero swappiness to >>>> prevent swapping at all [4]. >>>> >>>> [1] >>>> https://docs.datastax.com/en/cassandra-oss/3.x/cassandra/install/installRecommendSettings.html#Disableswap >>>> [2] >>>> https://github.com/apache/cassandra/blob/738dfde73560d289218f3afa4103a37e9f401757/src/java/org/apache/cassandra/utils/SigarLibrary.java#L172 >>>> [3] >>>> https://docs.kernel.org/admin-guide/sysctl/vm.html?highlight=swappiness#swappiness >>>> >>>> [4] >>>> https://www.ibm.com/docs/en/linux-on-systems?topic=settings-setting-swappiness-parameter-zero >>>> >>>> >>>> On 27. Jul 2023, at 10:14, manish khandelwal < >>>> manishkhandelwa...@gmail.com> wrote: >>>> >>>> Has anybody seen issues running Cassandra on RHEL 8.6. I am seeing >>>> performance dip while running Cassandra on RHEL8.6. Also with RHEL I am >>>> seeing swapping happening in spite of a lot of free memory available. In >>>> RHEL 7.9 we did not see any swapping with same workload and same RPM of >>>> Cassandra. Anyone running Cassandra on RHEL? >>>> >>>> Regards >>>> Manish >>>> >>>> >>>>
