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From Franc Carter <franc.car...@sirca.org.au>
Subject Re: reads/s suddenly dropped
Date Sun, 19 Feb 2012 20:31:07 GMT
On Mon, Feb 20, 2012 at 4:10 AM, Philippe <watcherfr@gmail.com> wrote:

> Perhaps your dataset can no longer be held in memory. Check iostats
>

I have been flushing the keycache and dropping the linux disk caches before
each to avoid testing memory reads.

One possibility that I thought of is that the success keys are now 'far
enough away' that they are not being included in the previous read and
hence the seek penalty has to be paid a lot more often  - viable ?

cheers

>  Le 19 févr. 2012 11:24, "Franc Carter" <franc.carter@sirca.org.au> a
> écrit :
>
>
>> I've been testing Cassandra - primarily looking at reads/second for our
>> fairly data model - one unique key with a row of columns that we always
>> request. I've now setup the cluster with with m1.large (2 cpus 8GB)
>>
>> I had loaded a months worth of data in and was doing random requests as a
>> torture test - and getting very nice results. I then loaded another days
>> worth of day and repeated the tests while the load was running - still good.
>>
>> I then started loading more days and at some point the performance
>> dropped by close to an order of magnitude ;-(
>>
>> Any ideas on what to look for ?
>>
>> thanks
>>
>> --
>>
>> *Franc Carter* | Systems architect | Sirca Ltd
>>  <marc.zianideferranti@sirca.org.au>
>>
>> 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
>>
>>


-- 

*Franc Carter* | Systems architect | Sirca Ltd
 <marc.zianideferranti@sirca.org.au>

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

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