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Posted to user@cassandra.apache.org by David Dabbs <dm...@gmail.com> on 2010/03/09 00:52:58 UTC

Cassandra latency question

Hello. I've been running the vPork load generator against two Cassandra
nodes running in VMs.
I'm running a trunk build with W=2 and R=1 and out-of-the-box JVM_OPTS which
should be fine, 
or so I thought. Throughput is lower than I expected. Are my expectations
out-of-line?

Thanks,

David


Writing results to: /home/vpork/results/30-thread-pork-39
 NumThreads      : 30
 Iterations      : 2000
 ReadOdds        : 0.8
 WriteOdds       : 0.1
 RewriteOdds     : 0.1
 Data Size       : 24000 B
 Nodes file given: [configs/cassandra/nodes.conf]
 Attempting to read nodes file: /home/vpork/configs/cassandra/nodes.conf
 Using node: dev-a01
 Using node: dev-a02
 Testing if our store even works ...
 %0.50   num=1 rGB=0.00 wGB=0.00 rFail=0 wFail=0 notFound=0
 -------------
 Elapsed time:  2.71 sec

 Writes:
   Num Writes:           202
   Write Throughput:     74.54 writes / sec
   Write Failures:       0
   Write Latency:        125.78 ms
   Write Latency (%99):  454.67 ms
   Write Latency stdDev: 102.78
   Bytes Written:        4.62 MB
   Thread w/Throughput:  0.19 KB / sec
   Total w/Throughput:   1747.00 KB / sec

 Reads:
   Num Read:             1602
   Read Throughput:      591.14 reads / sec
   Read Failures:        0
   Read Latency:         30.57 ms
   Read Latency (%99):   273.68 ms
   Read Latency stdDev:  50.19
   Read Not Found:       29 (%1.81)
   Bytes Read:           20.19 MB
   Thread r/Throughput:  0.77 KB / sec
   Total r/Throughput:   7628.00 KB / sec

Re: Cassandra latency question

Posted by Jonathan Ellis <jb...@gmail.com>.

something is screwed up if writes are 10x slower than reads

On Mon, Mar 8, 2010 at 5:52 PM, David Dabbs <dm...@gmail.com> wrote:
>
> Hello. I've been running the vPork load generator against two Cassandra
> nodes running in VMs.
> I'm running a trunk build with W=2 and R=1 and out-of-the-box JVM_OPTS which
> should be fine,
> or so I thought. Throughput is lower than I expected. Are my expectations
> out-of-line?
>
> Thanks,
>
> David
>
>
> Writing results to: /home/vpork/results/30-thread-pork-39
>  NumThreads      : 30
>  Iterations      : 2000
>  ReadOdds        : 0.8
>  WriteOdds       : 0.1
>  RewriteOdds     : 0.1
>  Data Size       : 24000 B
>  Nodes file given: [configs/cassandra/nodes.conf]
>  Attempting to read nodes file: /home/vpork/configs/cassandra/nodes.conf
>  Using node: dev-a01
>  Using node: dev-a02
>  Testing if our store even works ...
>  %0.50   num=1 rGB=0.00 wGB=0.00 rFail=0 wFail=0 notFound=0
>  -------------
>  Elapsed time:  2.71 sec
>
>  Writes:
>   Num Writes:           202
>   Write Throughput:     74.54 writes / sec
>   Write Failures:       0
>   Write Latency:        125.78 ms
>   Write Latency (%99):  454.67 ms
>   Write Latency stdDev: 102.78
>   Bytes Written:        4.62 MB
>   Thread w/Throughput:  0.19 KB / sec
>   Total w/Throughput:   1747.00 KB / sec
>
>  Reads:
>   Num Read:             1602
>   Read Throughput:      591.14 reads / sec
>   Read Failures:        0
>   Read Latency:         30.57 ms
>   Read Latency (%99):   273.68 ms
>   Read Latency stdDev:  50.19
>   Read Not Found:       29 (%1.81)
>   Bytes Read:           20.19 MB
>   Thread r/Throughput:  0.77 KB / sec
>   Total r/Throughput:   7628.00 KB / sec
>
>
>
>
>