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From Shuai Yuan <>
Subject writing speed test
Date Tue, 01 Jun 2010 06:18:31 GMT
Hi all,

I'm testing writing speed of cassandra with 4 servers. I'm confused by
the behavior of cassandra.

load-data app written in c++, using libcassandra (w/ modified batch
20 writing threads in 2 processes running on 2 servers

1.turn log level to INFO
2.JVM has 8G heap
3.32 concurrent read & 128 write in storage-conf.xml, other cache
enlarged as well.

1-monitoring by `date;nodetool -h host ring`
I add all load together and measure the writing speed by
(load_difference / time_difference), and I get about 15MB/s for the
whole cluster.

2-monitoring by `iostat -m 10`
I can watch the disk_io from the system level and have about 10MB/s -
65MB/s for a single machine. Very big variance over time.

3-monitoring by `iptraf -g`
In this way I watch the communication between servers and get about
10MB/s for a single machine.

So, have you checked the writing speed of cassandra? I feel it's quite
slow currently.

Could anyone confirm this is the normal writing speed of cassandra, or
please provide someway of improving it?

Shuai Yuan 袁帅
Supertool Corp. 北京学之途网络科技有限公司

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