Hi Piotrek, your disks are mostly idle as far as I can see (the one with 17% busy isn't that high on load). One thing came up to my mind did you look on the sizes of your sstables? I did this with something like
find /var/lib/cassandra/data -type f -size -1k -name "*Data.db" | wc find /var/lib/cassandra/data -type f -size -10k -name "*Data.db" | wc find /var/lib/cassandra/data -type f -size -100k -name "*Data.db" | wc ... find /var/lib/cassandra/data -type f -size -1000000k -name "*Data.db" | wc Your count is growing from opscenter - and if there are many really small tables I would guess you are running out of heap. If memory pressure is high it is likely that there will be much flushes of memtables to disk with many small files - had this once. You can increase heap in cassandra-env.sh, but be careful. Best regards, Roland
