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From Keith Freeman <>
Subject Re: heavy insert load overloads CPUs, with MutationStage pending
Date Wed, 11 Sep 2013 20:05:59 GMT
Thanks, I had seen your stackoverflow post.  I've got hundreds of 
(wide-) rows, and the writes are pretty well distributed across them.  
I'm very reluctant to drop back to the thrift interface.

On 09/11/2013 10:46 AM, Paul Cichonski wrote:
> How much of the data you are writing is going against the same row key?
> I've experienced some issues using CQL to write a full wide-row at once (across multiple
threads) that exhibited some of the symptoms you have described (i.e., high cpu, dropped mutations).
> This question goes into it a bit more:
 . I was able to solve my issue by switching to using the thrift batch_mutate to write a full
wide-row at once instead of using many CQL INSERT statements.
> -Paul
>> -----Original Message-----
>> From: Keith Freeman []
>> Sent: Wednesday, September 11, 2013 9:16 AM
>> Subject: Re: heavy insert load overloads CPUs, with MutationStage pending
>> On 09/10/2013 11:42 AM, Nate McCall wrote:
>>> With SSDs, you can turn up memtable_flush_writers - try 3 initially (1
>>> by default) and see what happens. However, given that there are no
>>> entries in 'All time blocked' for such, they may be something else.
>> Tried that, it seems to have reduced the loads a little after everything
>> warmed-up, but not much.
>>> How are you inserting the data?
>> A java client on a separate box using the datastax java driver, 48 threads
>> writing 100 records each iteration as prepared batch statements.
>> At 5000 records/sec, the servers just can't keep up, so the client backs up.
>> That's only 5M of data/sec, which doesn't seem like much.  As I mentioned,
>> switching to SSDs didn't help much, so I'm assuming at this point that the
>> server overloads are what's holding up the client.

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