Each table in the cluster will have a memtable. This is why you do not want to fracture the memory into 900+ slices. The rule of thumb I have followed is to stay in the low hundreds (maybe 200) tables for the whole cluster. I would be requiring the hard refactoring (or moving tables to different clusters) immediately, since you really need to reduce by at least 700 tables. You are seeing the memory impacts.
In addition, in my experience, CMS is much harder to tune. G1GC works well in my use cases without much tuning (or Java-guru level knowledge). However, I don’t think that you will be able to engineer around the 900+ tables, no matter which GC you use. Sean Durity – Staff Systems Engineer, Cassandra From: Luca Rondanini <luca.rondan...@gmail.com> Sent: Monday, July 19, 2021 11:34 AM To: user@cassandra.apache.org Subject: [EXTERNAL] R/W timeouts VS number of tables in keyspace Hi all, I have a keyspace with almost 900 tables. Lately I started receiving lots of w/r timeouts (eg com.datastax.driver.core.exceptions.Read/WriteTimeoutException: Cassandra timeout during write query at consistency LOCAL_ONE (1 replica were required but only 0 acknowledged the write). I'm even experiencing nodes crashing. In the logs I get many warnings like: WARN [Service Thread]....GCInspector.java:282 - ConcurrentMarkSweep GC in 4025ms. CMS Old Ge n: 2141569800 -> 2116170568; Par Eden Space: 167772160 -> 0; Par Survivor Space: 20971520 -> 0 WARN [GossipTasks:1].....FailureDetector.java:288 - Not marking nodes down due to local pause of 5038005208 > 5000000000 I know 900 tables is a design error for C* but before a super painful refactoring I'd like to rule out any configuration problem. Any suggestion? Thanks a lot, Luca ________________________________ The information in this Internet Email is confidential and may be legally privileged. It is intended solely for the addressee. Access to this Email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. When addressed to our clients any opinions or advice contained in this Email are subject to the terms and conditions expressed in any applicable governing The Home Depot terms of business or client engagement letter. The Home Depot disclaims all responsibility and liability for the accuracy and content of this attachment and for any damages or losses arising from any inaccuracies, errors, viruses, e.g., worms, trojan horses, etc., or other items of a destructive nature, which may be contained in this attachment and shall not be liable for direct, indirect, consequential or special damages in connection with this e-mail message or its attachment.
