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Posted to user@cassandra.apache.org by Anurag Gujral <an...@gmail.com> on 2011/04/03 03:21:20 UTC
compaction behaviour
Hi All,
I have loaded data into cassandra using batch processing the
response times for reads are in the range of 0.8 ms but I am using SSDs. so
I expect the read times to be even faster.
Every time I run compaction the latency numbers reduce to 0.3 to 0.4ms , is
there a way I can run compaction once with some parameters
so that i can get the same numbers 0.3 to 0.4 ms for reads.
Please note that I am not loading the data again.
Thanks
Anurag
Re: compaction behaviour
Posted by aaron morton <aa...@thelastpickle.com>.
Is "nodetool compact" what you are looking for ?
Aaron
On 4 Apr 2011, at 05:35, Anurag Gujral wrote:
> Hi Zhu,
> I did not got that SSDs have read latency of 0.1ms.Since there is only one data file
> I would expect the read of any key to take 0.1ms may be I am missing something
> please explain.
> Thanks
> Anurag
>
> On Sun, Apr 3, 2011 at 5:01 AM, Zhu Han <sc...@gmail.com> wrote:
>
> best regards,
> Zhu Han
>
>
>
> On Sun, Apr 3, 2011 at 9:21 AM, Anurag Gujral <an...@gmail.com> wrote:
> Hi All,
> I have loaded data into cassandra using batch processing the response times for reads are in the range of 0.8 ms but I am using SSDs. so I expect the read times to be even faster.
>
> Does your working set fit in the memory? If so, SSD is not helpful to reduce the latency.
>
> Every time I run compaction the latency numbers reduce to 0.3 to 0.4ms , is there a way I can run compaction once with some parameters
> so that i can get the same numbers 0.3 to 0.4 ms for reads.
> Please note that I am not loading the data again.
>
> Thanks
> Anurag
>
>
Re: compaction behaviour
Posted by Anurag Gujral <an...@gmail.com>.
Hi Zhu,
I did not got that SSDs have read latency of 0.1ms.Since there
is only one data file
I would expect the read of any key to take 0.1ms may be I am missing
something
please explain.
Thanks
Anurag
On Sun, Apr 3, 2011 at 5:01 AM, Zhu Han <sc...@gmail.com> wrote:
>
> best regards,
> Zhu Han
>
>
>
> On Sun, Apr 3, 2011 at 9:21 AM, Anurag Gujral <an...@gmail.com>wrote:
>
>> Hi All,
>> I have loaded data into cassandra using batch processing the
>> response times for reads are in the range of 0.8 ms but I am using SSDs. so
>> I expect the read times to be even faster.
>>
>
> Does your working set fit in the memory? If so, SSD is not helpful to
> reduce the latency.
>
>
>> Every time I run compaction the latency numbers reduce to 0.3 to 0.4ms ,
>> is there a way I can run compaction once with some parameters
>> so that i can get the same numbers 0.3 to 0.4 ms for reads.
>> Please note that I am not loading the data again.
>>
>> Thanks
>> Anurag
>>
>
>
Re: compaction behaviour
Posted by Zhu Han <sc...@gmail.com>.
best regards,
Zhu Han
On Sun, Apr 3, 2011 at 9:21 AM, Anurag Gujral <an...@gmail.com>wrote:
> Hi All,
> I have loaded data into cassandra using batch processing the
> response times for reads are in the range of 0.8 ms but I am using SSDs. so
> I expect the read times to be even faster.
>
Does your working set fit in the memory? If so, SSD is not helpful to reduce
the latency.
> Every time I run compaction the latency numbers reduce to 0.3 to 0.4ms ,
> is there a way I can run compaction once with some parameters
> so that i can get the same numbers 0.3 to 0.4 ms for reads.
> Please note that I am not loading the data again.
>
> Thanks
> Anurag
>