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Date: Fri, 3 Feb 2012 11:44:55 -0800
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Subject: Re: WARN [Memtable] live ratio
From: Mohit Anchlia <mohitanchlia@gmail.com>
To: user@cassandra.apache.org
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On Fri, Feb 3, 2012 at 8:46 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
> You should come up with a way to reproduce so we can fix it. :)

This happens when server is idle for a while with not so much data and
then you start a load like 50 write and 50 read requests per sec. We
have 4 CF that we write to and then read from.
>
> On Fri, Feb 3, 2012 at 10:31 AM, Mohit Anchlia <mohitanchlia@gmail.com> w=
rote:
>> On Fri, Feb 3, 2012 at 7:32 AM, Jonathan Ellis <jbellis@gmail.com> wrote=
:
>>> It's a warn because it's nonsense for the JVM to report that an column
>>> + overhead, takes less space than just the column data itself.
>>>
>>
>> But is there any action we need to take, or worry about? We trigger
>> alerts based on WARN and ERROR. But if there is nothing to do then it
>> probably is just an INFO.
>>> On Tue, Jan 31, 2012 at 9:41 PM, Mohit Anchlia <mohitanchlia@gmail.com>=
 wrote:
>>>> I guess this is not really a WARN in that case.
>>>>
>>>> On Tue, Jan 31, 2012 at 4:29 PM, aaron morton <aaron@thelastpickle.com=
> wrote:
>>>>> The ratio is the ratio of serialised bytes for a memtable to actual J=
VM
>>>>> allocated memory. Using a ratio below 1 would imply the JVM is using =
less
>>>>> bytes to store the memtable in memory than it takes to store it on di=
sk
>>>>> (without compression).
>>>>>
>>>>> The ceiling for the ratio is 64.
>>>>>
>>>>> The ratio is calculated periodically so if the workload changes, such=
 as
>>>>> system start up, the number will lag behind. I would guess numbers le=
ss than
>>>>> 1 mean the memtable does not have any data.
>>>>>
>>>>> Cheers
>>>>>
>>>>> -----------------
>>>>> Aaron Morton
>>>>> Freelance Developer
>>>>> @aaronmorton
>>>>> http://www.thelastpickle.com
>>>>>
>>>>> On 1/02/2012, at 8:27 AM, Radim Kolar wrote:
>>>>>
>>>>>
>>>>> =A0but a ration of< =A01 may occur
>>>>>
>>>>> for column families with =A0a very high update to insert ratio.
>>>>>
>>>>> better to ask why minimum ratio is 1.0. What harm can be done with us=
ing <
>>>>> 1.0 ratio?
>>>>>
>>>>>
>>>
>>>
>>>
>>> --
>>> Jonathan Ellis
>>> Project Chair, Apache Cassandra
>>> co-founder of DataStax, the source for professional Cassandra support
>>> http://www.datastax.com
>
>
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of DataStax, the source for professional Cassandra support
> http://www.datastax.com