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 > > >
