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From aaron morton <aa...@thelastpickle.com>
Subject Re: Number of keyspaces
Date Tue, 22 May 2012 21:42:01 GMT
1 KS with 24 CF's will use roughly the same resources as 24 KS's with 1 CF. Each CF:

* loads the bloom filter for each SSTable
* samples the index for each sstable
* uses row and key cache
* has a current memtable and potentially memtables waiting to flush.
* had secondary index CF's

I would generally avoid a data model that calls for CF's to be added in response to new entities
or new data. Older data will move moved to larger files, and not included in compaction for
newer data.

Hope that helps. 

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 23/05/2012, at 3:31 AM, Luís Ferreira wrote:

> I have 24 keyspaces, each with a columns family and am considering changing it to 1 keyspace
with 24 CFs. Would this be beneficial?
> On May 22, 2012, at 12:56 PM, samal wrote:
> 
>> Not ideally, now cass has global memtable tuning. Each cf correspond to memory  in
ram. Year wise cf means it will be in read only state for next year, memtable  will still
consume ram.
>> 
>> On 22-May-2012 5:01 PM, "Franc Carter" <franc.carter@sirca.org.au> wrote:
>> On Tue, May 22, 2012 at 9:19 PM, aaron morton <aaron@thelastpickle.com> wrote:
>> It's more the number of CF's than keyspaces.
>> 
>> Oh - does increasing the number of Column Families affect performance ?
>> 
>> The design we are working on at the moment is considering using a Column Family per
year. We were thinking this would isolate compactions to a more manageable size as we don't
update previous years.
>> 
>> cheers
>>  
>> 
>> Cheers
>> 
>> -----------------
>> Aaron Morton
>> Freelance Developer
>> @aaronmorton
>> http://www.thelastpickle.com
>> 
>> On 22/05/2012, at 6:58 PM, R. Verlangen wrote:
>> 
>>> Yes, it does. However there's no real answer what's the limit: it depends on
your hardware and cluster configuration. 
>>> 
>>> You might even want to search the archives of this mailinglist, I remember this
has been asked before.
>>> 
>>> Cheers!
>>> 
>>> 2012/5/21 Luís Ferreira <zamith.28@gmail.com>
>>> Hi,
>>> 
>>> Does the number of keyspaces affect the overall cassandra performance?
>>> 
>>> 
>>> Cumprimentos,
>>> Luís Ferreira
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> -- 
>>> With kind regards,
>>> 
>>> Robin Verlangen
>>> www.robinverlangen.nl
>>> 
>> 
>> 
>> 
>> 
>> -- 
>> Franc Carter | Systems architect | Sirca Ltd
>> franc.carter@sirca.org.au | www.sirca.org.au
>> Tel: +61 2 9236 9118 
>> Level 9, 80 Clarence St, Sydney NSW 2000
>> PO Box H58, Australia Square, Sydney NSW 1215
>> 
> 
> Cumprimentos,
> Luís Ferreira
> 
> 
> 


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