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From aaron morton <aa...@thelastpickle.com>
Subject Re: high write load, with lots of updates, considerations? tomestombed data coming back to life
Date Thu, 25 Jul 2013 05:14:41 GMT
> I was watching some videos from the C* summit 2013 and I recall many people saying that
if you can some up with a design where you don't preform updates on rows, that would make
things easier (I believe it was because there would be less compaction).
No entirely true. 

There will always be compaction. But if you do updates there are overwrites which means there
is data on disk that is irrelevant and is not released until compaction get's to those files.


> Could old tomestombed data somehow come back to life?  I forget what scenerio brings
about old data (kinda scary!).
If you don't run repair on every node every gc_grace_seconds there is a chance of it happening.


Cheers

-----------------
Aaron Morton
Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 24/07/2013, at 4:22 AM, S Ahmed <sahmed1020@gmail.com> wrote:

> I was watching some videos from the C* summit 2013 and I recall many people saying that
if you can some up with a design where you don't preform updates on rows, that would make
things easier (I believe it was because there would be less compaction).
> 
> When building an Analytics (time series) app on top of C*, based on Twitters Rainbird
design (http://www.slideshare.net/kevinweil/rainbird-realtime-analytics-at-twitter-strata-2011),
this means there will be lots and lots of counters.
> 
> With lots of counters (updates), admin wise, what are some things to consider?
> 
> Could old tomestombed data somehow come back to life?  I forget what scenerio brings
about old data (kinda scary!).


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