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From "Jonathan Haddad" <jonathan.had...@gmail.com>
Subject Re: CPU Bound Writes
Date Sat, 20 Jul 2013 16:12:11 GMT
Everything is written to the commit log. In the case of a crash, cassandra recovers by replaying
the log.

On Sat, Jul 20, 2013 at 9:03 AM, Mohammad Hajjat <hajjat@purdue.edu>
wrote:

> 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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