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From Wei Zhu <>
Subject Re: any way to get the #writes/second, reads per second
Date Tue, 14 May 2013 16:06:25 GMT
We have a long running script which wakes up every minute to get reads/writes through JMX.
It does the calculation to get r/s and w/s and send them to ganglia. We are thinking of using
graphite which comes with some sort of intelligence mentioned by Tomàs, but it's just too
big of a change for our infrastructure. 


----- Original Message -----

From: "Dean Hiller" <> 
Sent: Tuesday, May 14, 2013 4:37:14 AM 
Subject: Re: any way to get the #writes/second, reads per second 

Cool, thanks, 

From: Tomàs Núnez <<>>

Reply-To: "<>" <<>>

Date: Tuesday, May 14, 2013 4:53 AM 
To: user <<>> 
Subject: Re: any way to get the #writes/second, reads per second 

Yes, there isn't any place in the JMX with reads/second or writes/second, just CompletedTasks.
I send this info to Graphite ( and use the "derivative" function
to get reads/minute. Munin also does the trick ( But
you can't do that with cassandra itself, you need somewhere to make the calculations (cacti
is also a good match). 

Hope that helps. There is some more information about monitoring this kind of things here:

2013/5/13 Hiller, Dean <<>> 
We running a pretty consistent load on our cluster and added a new node to a 6 node cluster
Friday(QA worked great, but production not so much). One mistake that was made was starting
up the new node, then disabling the firewall :( which allowed nodes to discover it BEFORE
the node bootstrapped itself. We shutdown the node and booted him up and he bootstrapped himself
streaming all the data in. 

After that though, all the ndoes have really really high load numbers now. We are trying to
figure out what is going on still. 

Is there any way to get the number of reads/second and writes/second through JMX or something?
The only way I can see of on doing this is manually calculating it by timing the read count
and dividing by my manual stop watches start/stop times(timerange). 

Also, while my load is load average: 20.31, 19.10, 19.72 , what does a normal iostat look
like? My iostat await time is 13.66 ms which I think is kind of bad, but not that bad to cause
a load of 20.31? 

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util 
sda 0.02 0.07 11.70 1.96 1353.67 702.88 150.58 0.19 13.66 3.61 4.93 
sdb 0.00 0.02 0.11 0.46 20.72 97.54 206.70 0.00 1.33 0.67 0.04 


Tomàs Núñez 
Tel. + 34 93 159 31 00 
Fax. + 34 93 396 18 52 
Llull, 95-97, 2º planta, 08005 Barcelona 
Skype: tomas.nunez.groupalia<> 
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