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From Philippe <watche...@gmail.com>
Subject Re: Writes slower then reads
Date Thu, 05 Jan 2012 13:38:31 GMT
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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