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Posted to user@cassandra.apache.org by James Briggs <ja...@yahoo.com.INVALID> on 2019/02/16 03:42:01 UTC

Cassandra vnodes Streaming Reliability Calculator

Hi folks.

Please check out my online vnodes reliability calculator and reply with any feedback:http://www.jebriggs.com/blog/2019/02/cassandra-vnodes-reliability-calculator/
Thanks, James Briggs.
--
Cassandra/MySQL DBA. Available in Bay Area or remote.
cass_top: https://github.com/jamesbriggs/cassandra-top

Re: Cassandra vnodes Streaming Reliability Calculator

Posted by James Briggs <ja...@yahoo.com.INVALID>.
Hi Ken.
1) Thanks for the great link.
Ironically it was written by Netflix, who continued to use single tokenfor years after vnodes were released so that they could continue touse Priam and their other tools dependent on single token. (I was in theearly Cassandra group there.)

2) My tool agrees overall with their findings:
a) it does reflect that increasing numbers of vnodes and nodes reduce reliabilitydramatically, so the results are conceptually the same and the deltas atdifferent vnode counts matches what I see in my calculator.

b) but it uses a more complicated model. I'm happy with my calculator thatlooks at simple "probability of a streaming connection failed for any reason"and is immediately usable by any DBA or SRE.

3) As an Operations DBA, their reference to "centuries" made me laugh though.Note that my calculations are about failures within one week, which alignsmore with my experience. So either they're overly optimistic, or I'm pessimistic.
You can verify which by doing a grep of your logs on a production cluster fora month and counting how many connection failures there were. My blogpost has some links to actual error message to grep for. 4) Note that Datastax recommends 8 vnodes now. See my blog for the reference.
Thanks, James Briggs.
--
Cassandra/MySQL DBA. Available in Bay area or remote.
cass_top: https://github.com/jamesbriggs/cassandra-top

      From: Kenneth Brotman <ke...@yahoo.com.INVALID>
 To: user@cassandra.apache.org 
 Sent: Saturday, February 16, 2019 5:00 AM
 Subject: RE: Cassandra vnodes Streaming Reliability Calculator
   
#yiv4674113709 #yiv4674113709 -- _filtered #yiv4674113709 {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;} _filtered #yiv4674113709 {font-family:Tahoma;panose-1:2 11 6 4 3 5 4 4 2 4;}#yiv4674113709 #yiv4674113709 p.yiv4674113709MsoNormal, #yiv4674113709 li.yiv4674113709MsoNormal, #yiv4674113709 div.yiv4674113709MsoNormal {margin:0in;margin-bottom:.0001pt;font-size:12.0pt;font-family:New;}#yiv4674113709 a:link, #yiv4674113709 span.yiv4674113709MsoHyperlink {color:blue;text-decoration:underline;}#yiv4674113709 a:visited, #yiv4674113709 span.yiv4674113709MsoHyperlinkFollowed {color:purple;text-decoration:underline;}#yiv4674113709 span.yiv4674113709EmailStyle17 {color:#1F497D;}#yiv4674113709 .yiv4674113709MsoChpDefault {font-size:10.0pt;} _filtered #yiv4674113709 {margin:1.0in 1.0in 1.0in 1.0in;}#yiv4674113709 div.yiv4674113709WordSection1 {}#yiv4674113709 Hi James,  Thanks for doing that.  Very interesting.  I haven’t had a chance to check the math.  Did you look at this white paper by Lynch and Snyder called Cassandra Availability with Virtual Nodes: https://github.com/jolynch/python_performance_toolkit/blob/master/notebooks/cassandra_availability/whitepaper/cassandra-availability-virtual.pdf  Are the calculations consistent with your online calculator?  Thanks again,  Kenneth Brotman  From: James Briggs [mailto:james.briggs@yahoo.com.INVALID] 
Sent: Friday, February 15, 2019 7:42 PM
To: user@cassandra.apache.org
Subject: Cassandra vnodes Streaming Reliability Calculator  Hi folks.



Please check out my online vnodes reliability calculator and reply with any feedback:http://www.jebriggs.com/blog/2019/02/cassandra-vnodes-reliability-calculator/  Thanks, James Briggs.
--
Cassandra/MySQL DBA. Available in Bay Area or remote.
cass_top: https://github.com/jamesbriggs/cassandra-top

RE: Cassandra vnodes Streaming Reliability Calculator

Posted by Kenneth Brotman <ke...@yahoo.com.INVALID>.
Hi James,

 

Thanks for doing that.  Very interesting.  I haven’t had a chance to check the math.  Did you look at this white paper by Lynch and Snyder called Cassandra Availability with Virtual Nodes: https://github.com/jolynch/python_performance_toolkit/blob/master/notebooks/cassandra_availability/whitepaper/cassandra-availability-virtual.pdf

 

Are the calculations consistent with your online calculator?

 

Thanks again,

 

Kenneth Brotman

 

From: James Briggs [mailto:james.briggs@yahoo.com.INVALID] 
Sent: Friday, February 15, 2019 7:42 PM
To: user@cassandra.apache.org
Subject: Cassandra vnodes Streaming Reliability Calculator

 

Hi folks.







Please check out my online vnodes reliability calculator and reply with any feedback:

http://www.jebriggs.com/blog/2019/02/cassandra-vnodes-reliability-calculator/

 

Thanks, James Briggs.
--
Cassandra/MySQL DBA. Available in Bay Area or remote.
cass_top: https://github.com/jamesbriggs/cassandra-top