Hi, We run 48 node cluster that stores counts in wide rows. Each node is using roughly 1TB space on a 2TB EBS gp2 drive for data directory and LeveledCompactionStrategy. We have been trying to bootstrap new nodes that use a raid0 configuration over 2 1TB EBS drives to increase I/O throughput cap from 160 MB/s to 250 MB/s (AWS limits). Every time a node finishes streaming it is bombarded by a large number of compactions. We see CPU load on the new node spike extremely high and CPU load on all the other nodes in the cluster drop unreasonably low. Meanwhile our app's latency for writes to this cluster average 10 seconds or greater. We've already tried throttling compaction throughput to 1 mbps and we've always had concurrent_compactors set to 2 but the disk is still saturated. In every case we have had to shut down the Cassandra process on the new node to resume acceptable operations.
We're currently upgrading all of our clients to use the 3.11.0 version of the DataStax Python driver, which will allow us to add our next newly bootstrapped node to a blacklist, hoping that if it doesn't accept writes the rest of the cluster can serve them adequately (as is the case whenever we turn down the bootstrapping node), and allow it to finish its compactions. We were also interested in hearing if anyone has had much luck using the sstableofflinerelevel tool, and if this is a reasonable approach for our issue. One of my colleagues found a post where a user had a similar issue and found that bloom filters had an extremely high false positive ratio, and although I didn't check that during any of these attempts to bootstrap it seems to me like if we have that many compactions to do we're likely to observe that same thing. Would appreciate any guidance anyone can offer. Thanks, Paul
