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From "R. Verlangen" <ro...@us2.nl>
Subject Re: Writes slower then reads
Date Thu, 05 Jan 2012 13:54:02 GMT
I'm also reading with CL = ONE

2012/1/5 Philippe <watcherfr@gmail.com>

> Depending on the CL you're reading at it will yes : if the CL requires
> that the "slow" node create a digest of the data and send it to the
> coordinator then it might explain the poor performance on reads. What is
> your read CL ?
>
> 2012/1/5 R. Verlangen <robin@us2.nl>
>
> As I posted this I noticed that the other node's CPU is running high on
>> some other cronjobs (every couple of minutes to 60% usage). Is the lack of
>> more CPU cycles a problem in this case?
>>
>> Robin
>>
>> 2012/1/5 R. Verlangen <robin@us2.nl>
>>
>> CPU is idle (< 10% usage). Disk reads occasionally blocks over 32/64K.
>>> Writes around 0-5MB per second. Network traffic 0.1 / 0.1 MB/s (in / out).
>>> Paging 0. System int ~ 1300, csw ~ 2500.
>>>
>>>
>>> 2012/1/5 Philippe <watcherfr@gmail.com>
>>>
>>>> What can you see in vmstat/dstat ?
>>>> Le 5 janv. 2012 11:58, "R. Verlangen" <robin@us2.nl> a écrit :
>>>>
>>>> Hi there,
>>>>>
>>>>> I'm running a cassandra 0.8.6 cluster with 2 nodes (in 2 DC's), RF =
>>>>> 2. Actual data on the nodes is only 1GB. Disk latency < 1ms. Disk
>>>>> throughput ~ 0.4MB/s. OS load always below 1 (on a 8 core machine with
16GB
>>>>> ram).
>>>>>
>>>>> When I'm running my writes against the cluster with cl = ONE all reads
>>>>> appear to be faster then the writes.
>>>>>
>>>>> Average write speed = 1600us/operation
>>>>> Average read speed = 200us/operation
>>>>>
>>>>> I'm really wondering why this is the case. Anyone got a clue?
>>>>>
>>>>> With kind regards,
>>>>> Robin
>>>>>
>>>>
>>>
>>
>

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