Also, I just restarted my Cassandra process by setting "disk_access_mode: mmap_index_only" and I still see the same WARN message, I believe it's just a startup check and doesn't rely on the disk_access_mode value
WARN [main] 2021-04-16 00:08:00,088 StartupChecks.java:311 - Maximum > number of memory map areas per process (vm.max_map_count) 65530 is too low, > recommended value: 1048575, you can change it with sysctl. On Thu, Apr 15, 2021 at 4:45 PM Jai Bheemsen Rao Dhanwada < jaibheem...@gmail.com> wrote: > Thank you Kane and Jeff. > > can I survive with a low mmap value of 65530 with "disk_acces_mode = > mmap_index_only" ? does this hold true even for higher workloads with > larger datasets like ~1TB per node? > > On Thu, Apr 15, 2021 at 4:43 PM Jeff Jirsa <jji...@gmail.com> wrote: > >> disk_acces_mode = mmap_index_only to use fewer maps (or disable it >> entirely as appropriate). >> >> >> >> On Thu, Apr 15, 2021 at 4:42 PM Kane Wilson <k...@raft.so> wrote: >> >>> Cassandra mmaps SSTables into memory, of which there can be many files >>> (including all their indexes and what not). Typically it'll do so greedily >>> until you run out of RAM. 65k map areas tends to be quite low and can >>> easily be exceeded - you'd likely need very low density nodes to avoid >>> going over 65k, and thus you'd require lots of nodes (making management >>> harder). I'd recommend figuring out a way to up your limits as the first >>> course of action. >>> >>> raft.so - Cassandra consulting, support, and managed services >>> >>> >>> On Fri, Apr 16, 2021 at 4:29 AM Jai Bheemsen Rao Dhanwada < >>> jaibheem...@gmail.com> wrote: >>> >>>> Hello All, >>>> >>>> The recommended settings for Cassandra suggests to have a higher value >>>> for vm.max_map_count than the default 65530 >>>> >>>> WARN [main] 2021-04-14 19:10:52,528 StartupChecks.java:311 - Maximum >>>>> number of memory map areas per process (vm.max_map_count) 65530 is >>>>> too low, recommended value: 1048575, you can change it with sysctl. >>>> >>>> >>>> However, I am running Cassandra process as a container, where I don't >>>> have access to change the value on Kubernetes worker node and the cassandra >>>> pod runs with less privileges. I would like to understand why Cassandra >>>> needs a higher value of memory map? and is there a way to restrict >>>> Cassandra to not use beyond the default value of 65530. If there is a way >>>> please let me know how to restrict and also any side effects in making that >>>> change? >>>> >>>> Thanks in advance >>>> >>>