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From Batranut Bogdan <>
Subject Re: Compaction throrheling
Date Thu, 24 Apr 2014 21:16:39 GMT
I have CPU to spare but reached hdd limit.
Well this might deserve it's own conversation thread....  but I did reach the limit of IO
after after using a wide row and counter columnfamily ... def looks like this:

a int , b int, c string , timestamp int, d counter, e counter f counter, g counter PK ((a,b,c)

 After 200 mil PKs and 6 Timestamps for each of them my whole 8 core XEON, 32 Gb ram, 6 server
 cluster went into medium to high load (according to opscenter) and the hdds load was ~ 100%
according to iostat. 

But that is something else. 

I asked the question since my cluster is not under heavy load and I see compactions done with
4 MBs / sec (for big files according to my observations) and compactions done with 40 MBs/s
for smaller ones. I need C* to do compactions as fast as possible if the system is not under
On Friday, April 25, 2014 12:06 AM, Robert Coli <> wrote:
On Thu, Apr 24, 2014 at 1:54 PM, Batranut Bogdan <> wrote:

Is this a setting that will have an impact only on fast cpu + ssd ?

It's a setting that will only have impact if you have CPU or IO to spare. You don't need a
fast CPU or SSD to meet those conditions.

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