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From "" <>
Subject Re: cassandra slows down after inserts
Date Mon, 13 Jul 2009 13:06:13 GMT
how do i find out if JVM is GCing?

On Sun, Jul 12, 2009 at 10:37 PM, Sandeep Tata <>wrote:

> What hardware are you running one?

 dual quadcore intel xeon 2.0 ghz, 32GB ram, and hardware raid config
operating system is fedora core 9

How long does the slowdown last ?

i stopped inserting data after slowdown starts, and it is still slow now
after over 10 hours.
however if i stop cassandra and start it, it becomes super fast immediately.
till i insert another 100k or so rows when it becomes really slow again.

>  There are a few reasons for temporary slowdowns ... perhaps the JVM
> started GCing?

how do i find out if this is the cause?

> Cassandra spends time cleaning up the on-disk SSTables
> in a process called compaction. This could cause the client to observe
> a slowdown.
> Things you could try --
> Reduce the Memtable size in the config files. (If GCing was the problem)
> Increasing the number of SSTables written before compaction kicks in.

can you tell me what numbers i should use?


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