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From Franc Carter <franc.car...@sirca.org.au>
Subject Re: keycache persisted to disk ?
Date Mon, 13 Feb 2012 08:14:47 GMT
2012/2/13 R. Verlangen <robin@us2.nl>

> This is because of the "warm up" of Cassandra as it starts. On a start it
> will start fetching the rows that were cached: this will have to be loaded
> from the disk, as there is nothing in the cache yet. You can read more
> about this at  http://wiki.apache.org/cassandra/LargeDataSetConsiderations
>


I actually has the opposite 'problem'. I have a pair of servers that have
been static since mid last week, but have seen performance vary
significantly (x10) for exactly the same query. I hypothesised it was
various caches so I shut down Cassandra, flushed the O/S buffer cache and
then bought it back up. The performance wasn't significantly different to
the pre-flush performance

cheers


>
>
> 2012/2/13 Franc Carter <franc.carter@sirca.org.au>
>
>> On Mon, Feb 13, 2012 at 5:03 PM, zhangcheng <zhangcheng@jike.com> wrote:
>>
>>> **
>>>
>>> I think the keycaches and rowcahches are bothe persisted to disk when
>>> shutdown, and restored from disk when restart, then improve the performance.
>>>
>>
>> Thanks - that would explain at least some of what I am seeing
>>
>> cheers
>>
>>
>>>
>>> 2012-02-13
>>> ------------------------------
>>>  zhangcheng
>>> ------------------------------
>>> *发件人:* Franc Carter
>>> *发送时间:* 2012-02-13  13:53:56
>>> *收件人:* user
>>> *抄送:*
>>> *主题:* keycache persisted to disk ?
>>>
>>> Hi,
>>>
>>> I am testing Cassandra on Amazon and finding performance can vary fairly
>>> wildly. I'm leaning towards it being an artifact of the AWS I/O system but
>>> have one other possibility.
>>>
>>> Are keycaches persisted to disk and restored on a clean shutdown and
>>> restart ?
>>>
>>> cheers
>>>
>>> --
>>>
>>> *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
>>
>>
>


-- 

*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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