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Posted to user@cassandra.apache.org by Mark Jones <MJ...@imagehawk.com> on 2010/04/07 21:16:42 UTC
Can these stats be right?
>From cfstats:
SSTable count: 3
Space used (live): 4951669191
Space used (total): 5237040637
Memtable Columns Count: 190266
Memtable Data Size: 23459012
Memtable Switch Count: 89
Read Count: 0
Read Latency: NaN ms.
Write Count: 13307292
Write Latency: 0.045 ms.
Pending Tasks: 0
Key cache capacity: 200000
Key cache size: 0
Key cache hit rate: NaN
Row cache: disabled
Compacted row minimum size: 446
Compacted row maximum size: 111524663
Compacted row mean size: 880
A Write Latency of .045 ms should translate into > 22,000 writes per second, yet my 80 threads pumping data at this node, do good to get to 6000/second and the machine sending the writes is 97% idle.
I have 3 nodes, with a replication factor of 2.
Re: Can these stats be right?
Posted by Rob Coli <rc...@digg.com>.
On 4/7/10 12:16 PM, Mark Jones wrote:
> Read Latency: NaN ms.
./trunk/src/java/org/apache/cassandra/tools/NodeCmd.java
"
outs.println("\t\tRead Latency: " + String.format("%01.3f",
cfstore.getRecentReadLatencyMicros() / 1000) + "
"
This call is telling you the (Read|Write|Range)Latency since the last
time it was sampled. The other measure of latency is a value since the
node started, exposed via the JMX interface as
"org.apache.cassandra.service.StorageProxy.Attributes.TotalRangeLatencyMicros".
If you are sure to not restart your node while doing your testing, this
should provide you with the latency number you are looking for.
http://wiki.apache.org/cassandra/JmxInterface#org.apache.cassandra.service.StorageProxy.Attributes.TotalRangeLatencyMicros
The JmxInterface wiki page is currently missing a section on the per-CF
attributes, but as cfstats shows, they are available via the JMX
interface as well.
=Rob