Hi there,
I'm running a cassandra 0.8.6 cluster with 2 nodes (in 2 DC's), RF = 2.
Actual data on the nodes is only 1GB. Disk latency 1ms. Disk throughput ~
0.4MB/s. OS load always below 1 (on a 8 core machine with 16GB ram).
When I'm running my writes against the cluster with cl = ONE all reads
What can you see in vmstat/dstat ?
Le 5 janv. 2012 11:58, R. Verlangen ro...@us2.nl a écrit :
Hi there,
I'm running a cassandra 0.8.6 cluster with 2 nodes (in 2 DC's), RF = 2.
Actual data on the nodes is only 1GB. Disk latency 1ms. Disk throughput ~
0.4MB/s. OS load always below 1 (on a 8
As I posted this I noticed that the other node's CPU is running high on
some other cronjobs (every couple of minutes to 60% usage). Is the lack of
more CPU cycles a problem in this case?
Robin
2012/1/5 R. Verlangen ro...@us2.nl
CPU is idle ( 10% usage). Disk reads occasionally blocks over
Depending on the CL you're reading at it will yes : if the CL requires that
the slow node create a digest of the data and send it to the coordinator
then it might explain the poor performance on reads. What is your read CL ?
2012/1/5 R. Verlangen ro...@us2.nl
As I posted this I noticed that the
I'm also reading with CL = ONE
2012/1/5 Philippe watche...@gmail.com
Depending on the CL you're reading at it will yes : if the CL requires
that the slow node create a digest of the data and send it to the
coordinator then it might explain the poor performance on reads. What is
your read CL
What if you shutdown the cassandra service on the slow node, does that
improve your read performance ?
If it does then that sole node is responsible for the slow down because it
can't act as a coordinator fast enough.
2012/1/5 R. Verlangen ro...@us2.nl
I'm also reading with CL = ONE
2012/1/5
It does not appear to affect the response time, certainly not in a positive
way.
2012/1/5 Philippe watche...@gmail.com
What if you shutdown the cassandra service on the slow node, does that
improve your read performance ?
If it does then that sole node is responsible for the slow down because
You may be overloading the cluster though...
My hypothesis is that your traffic is being spread across your node and
that one slow node is slowing down the fraction of traffic that goes to
that node (when it's acting as coordinator).
So what I would do is reduce the read load a lot to make sure I
The write and read load is very minimal the moment. Roughly 10 writes + 10
reads / second. So 20 operations per second. Don't think that overloads my
cluster, does it?
2012/1/5 Philippe watche...@gmail.com
You may be overloading the cluster though...
My hypothesis is that your traffic is
Unless you are doing huge batches no... don't have any other idea for now...
2012/1/5 R. Verlangen ro...@us2.nl
The write and read load is very minimal the moment. Roughly 10 writes + 10
reads / second. So 20 operations per second. Don't think that overloads my
cluster, does it?
2012/1/5
What happens when you turn off the cron jobs ?
Cheers
-
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com
On 6/01/2012, at 6:57 AM, Philippe wrote:
Unless you are doing huge batches no... don't have any other idea for now...
2012/1/5 R. Verlangen
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