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From Ben Slater <>
Subject Re: Is it a memory issue?
Date Mon, 07 Nov 2016 03:41:49 GMT
This sounds to me like your writes go ahead of compactions trying to keep
up which can eventually cause issues. Keep an eye on nodetool
compactionstats if the number of compactions continually climbs then you
are writing faster than Cassandra can actually process. If this is
happening then you need to either add more processing capacity (nodes) to
your cluster or throttle writes on the client side.

It could also be related to conditions like an individual partition growing
too big but I’d check for backed up compactions first.


On Mon, 7 Nov 2016 at 14:17 <>

> Hi All,
> We have one issue on C* testing. At first the inserting was very fast and
> TPS was about 30K/s, but when the size of data rows reached 2 billion, the
> insertion rate decreased very badly and the TPS was 20K/s. When the size of
> rows reached 2.3 billion, the TPS decreased to 0.5K/s, and writing timeout
> come out. At last OOM issue happened in some nodes and C* deamon in some
> nodes crashed.  In production we have about 8 billion rows. My testing
> cluster setting is as below. My question is if the memory is the main
> issue. Do I need increase the memory, and what's the right setting for MAX_HEAP_SIZE
> My cluster setting:
> C* cluster with 3 nodes in Aliyun Cloud
> CPU: 4core
> Memory: 8G
> Disk: 500G
> My table schema:
> CREATE KEYSPACE IF NOT EXISTS cargts WITH REPLICATION = {'class': 'SimpleStrategy','replication_factor':2};
> use cargts;
> CREATE TABLE eventdata (
> deviceId int,
> date int,
> event_time bigint,
> lat decimal,
> lon decimal,
> speed int,
> heading int,
> PRIMARY KEY ((deviceId,date),event_time)
> )
> CREATE INDEX ON eventdata (event_time);
> Best Regards,
> -Simon Wu

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