May I suggest dstat, does cpu, memory, and io on one console
dstat -vn 3

So possible causes
 * Not sufficient parrallelism in the client
 * Server has too few threads
 * You are not CPU bound, network or disk may be the bottleneck 

p


----- Original Message -----
From: Kent Tong <freemant2...@yahoo.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
Cc: 
Sent: Thursday, 15 December 2011, 10:58
Subject: performance reaching plateau while the hardware is still idle

Hi,

I am running a performance test for Cassandra 1.0.5. It can perform about 1500 
business operation (one read+one write to the same row) per second. However, 
the CPU is still 85% idle (as shown by vmstat) and the IO utilization is less 
than a few percent (as shown by iostat). "nodetool tpstats" shows basically no 
active and pending threads. I can run several such test clients concurrently, 
achieving the same operations per second without increasing the hardware 
utilization. So, why the performance has reached a plateau while there is still 
idle hardware resources?


Thanks in advance for any idea!

Reply via email to