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 >>> >>> >>>
