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From Benyi Wang <bewang.t...@gmail.com>
Subject Re: Is it safe to change RF in this situation?
Date Thu, 08 Sep 2016 22:15:23 GMT
Thanks a lot. Will do as you suggested.

On Thu, Sep 8, 2016 at 3:08 PM, Hannu Kröger <hkroger@gmail.com> wrote:

> Ok, so I have to say that I’m not 100% sure how many replicas of data is
> it trying to maintain but it should not blow up (if repair crashes or
> something, it’s ok). So it should be safe to do.
>
> When the repair has run you can start with the plan I suggested and run
> repairs afterwards.
>
> Hannu
>
> On 8 Sep 2016, at 18:01, Benyi Wang <bewang.tech@gmail.com> wrote:
>
> Thanks. What about this situation:
>
> * Change RF 2 => 3
> * Start repair
> * Roll back RF 3 => 2
> * repair is still running
>
> I'm wondering what the repair is trying to do? The repair is trying to fix
> as RF=2 or still trying to fix like RF=3?
>
> On Thu, Sep 8, 2016 at 2:53 PM, Hannu Kröger <hkroger@gmail.com> wrote:
>
>> Yep, you can fix it by running repair or even faster by changing the
>> consistency level to local_quorum and deploying the new version of the app.
>>
>> Hannu
>>
>> On 8 Sep 2016, at 17:51, Benyi Wang <bewang.tech@gmail.com> wrote:
>>
>> Thanks Hannu,
>>
>> Unfortunately, we started changing RF from 2 to 3, and did see the empty
>> result rate is going higher. I assume that  "If the LOCAL_ONE read hit the
>> new replica which is not there yet, the CQL query will return nothing." Is
>> my assumption correct?
>>
>> On Thu, Sep 8, 2016 at 11:49 AM, Hannu Kröger <hkroger@gmail.com> wrote:
>>
>>> Hi,
>>>
>>> If you change RF=2 -> 3 first, the LOCAL_ONE reads might hit the new
>>> replica which is not there yet. So I would change LOCAL_ONE -> LOCAL_QUORUM
>>> first and then change the RF and then run the repair. LOCAL_QUORUM is
>>> effectively ALL in your case (RF=2) if you have just one DC, so you can
>>> change the batch CL later.
>>>
>>> Cheers,
>>> Hannu
>>>
>>> > On 8 Sep 2016, at 14:42, Benyi Wang <bewang.tech@gmail.com> wrote:
>>> >
>>> > * I have a keyspace with RF=2;
>>> > * The client read the table using LOCAL_ONE;
>>> > * There is a batch job loading data into the tables using ALL.
>>> >
>>> > I want to change RF to 3 and both the client and the batch job use
>>> LOCAL_QUORUM.
>>> >
>>> > My question is "Will the client still read the correct data when the
>>> repair is running at the time my batch job loading is running too?"
>>> >
>>> > Or should I change to LOCAL_QUORUM first?
>>> >
>>> > Thanks.
>>>
>>>
>>
>>
>
>

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