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From Mohammad Hajjat <haj...@purdue.edu>
Subject Re: CPU Bound Writes
Date Sat, 20 Jul 2013 16:02:00 GMT
Patricia,

Thanks for the info. So are you saying that the *whole* data is being
written on disk in the commit log, not just some sort of a summary/digest?
I'm writing 10MB objects and I'm noticing high latency (250 milliseconds
even with ANY consistency), so I guess that explains my high delays?

Thanks,
Mohammad


On Fri, Jul 19, 2013 at 2:17 PM, Patricia Gorla <gorla.patricia@gmail.com>wrote:

> Kanwar,
>
> This is because writes are appends to the commit log, which is stored on
> disk, not memory. The commit log is then flushed to the memtable (in
> memory), before being written to an sstable on disk.
>
> So, most of the actions in sending out a write are writing to disk.
>
> Also see: http://www.datastax.com/docs/1.2/dml/about_writes
>
> Patricia
>
>
> On Fri, Jul 19, 2013 at 1:05 PM, Kanwar Sangha <kanwar@mavenir.com> wrote:
>
>>  “Insert-heavy workloads will actually be CPU-bound in Cassandra before
>> being memory-bound”****
>>
>> ** **
>>
>> Can someone explain why the internals of why writes are CPU bound ?****
>>
>> ** **
>>
>> ** **
>>
>
>


-- 
*Mohammad Hajjat*
*Ph.D. Student*
*Electrical and Computer Engineering*
*Purdue University*

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