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From "R. Verlangen" <ro...@us2.nl>
Subject Re: keycache persisted to disk ?
Date Mon, 13 Feb 2012 08:20:03 GMT
I also noticed that, Cassandra appears to perform better under a continues
load.

Are you sure the rows you're quering are actually in the cache?

2012/2/13 Franc Carter <franc.carter@sirca.org.au>

> 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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