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Posted to user@cassandra.apache.org by Peng Xiao <25...@qq.com> on 2017/09/28 11:46:16 UTC
回复： data loss in different DC
even with CL=QUORUM,there is no guarantee to be sure to read the same data in DC2,right?
then multi DCs looks make no sense?
------------------ 原始邮件 ------------------
发件人: "DuyHai Doan";<do...@gmail.com>;
发送时间: 2017年9月28日(星期四) 下午5:45
收件人: "user"<us...@cassandra.apache.org>;
主题: Re: data loss in different DC
If you're writing into DC1 with CL = LOCAL_xxx, there is no guarantee to be sure to read the same data in DC2. Only repair will help you
On Thu, Sep 28, 2017 at 11:41 AM, Peng Xiao <25...@qq.com> wrote:
Dear All,
We have a cluster with one DC1:RF=3,another DC DC2:RF=1 only for ETL,but we found that sometimes we can query records in DC1,while not able not find the same record in DC2 with local_quorum.How it happens?
Could anyone please advise?
looks we can only run repair to fix it.
Thanks,
Peng Xiao
Re: 回复： data loss in different DC
Posted by Reynald Bourtembourg <re...@esrf.fr>.
Do you mean how often we should run repairs in this situation (write at
CL=EACH_QUORUM and CL=LOCAL_QUORUM)?
I don't consider myself as an expert in this domain, so I will let the
real experts answer to this question...
You can also refer to this mailing list history (many threads on this
snbject) and to the recommendations in the documentation:
http://cassandra.apache.org/doc/latest/operating/repair.html#usage-and-best-practices
Kind regards
Reynald
On 28/09/2017 14:49, Jacob Shadix wrote:
> How often are you running repairs?
>
> -- Jacob Shadix
>
> On Thu, Sep 28, 2017 at 7:53 AM, Reynald Bourtembourg
> <reynald.bourtembourg@esrf.fr <ma...@esrf.fr>>
> wrote:
>
> Hi,
>
> You can write with CL=EACH_QUORUM and read with CL=LOCAL_QUORUM to
> get strong consistency.
>
> Kind regards,
> Reynald
>
>
> On 28/09/2017 13:46, Peng Xiao wrote:
>> even with CL=QUORUM,there is no guarantee to be sure to read the
>> same data in DC2,right?
>> then multi DCs looks make no sense?
>>
>>
>> ------------------ 原始邮件 ------------------
>> *发件人:* "DuyHai Doan";<do...@gmail.com>
>> <ma...@gmail.com>;
>> *发送时间:* 2017年9月28日(星期四) 下午5:45
>> *收件人:* "user"<us...@cassandra.apache.org>
>> <ma...@cassandra.apache.org>;
>> *主题:* Re: data loss in different DC
>>
>> If you're writing into DC1 with CL = LOCAL_xxx, there is no
>> guarantee to be sure to read the same data in DC2. Only repair
>> will help you
>>
>> On Thu, Sep 28, 2017 at 11:41 AM, Peng Xiao <2535053@qq.com
>> <ma...@qq.com>> wrote:
>>
>> Dear All,
>>
>> We have a cluster with one DC1:RF=3,another DC DC2:RF=1 only
>> for ETL,but we found that sometimes we can query records in
>> DC1,while not able not find the same record in DC2 with
>> local_quorum.How it happens?
>> Could anyone please advise?
>> looks we can only run repair to fix it.
>>
>> Thanks,
>> Peng Xiao
>>
>>
>
>
Re: 回复： data loss in different DC
Posted by Jacob Shadix <ja...@gmail.com>.
How often are you running repairs?
-- Jacob Shadix
On Thu, Sep 28, 2017 at 7:53 AM, Reynald Bourtembourg <
reynald.bourtembourg@esrf.fr> wrote:
> Hi,
>
> You can write with CL=EACH_QUORUM and read with CL=LOCAL_QUORUM to get
> strong consistency.
>
> Kind regards,
> Reynald
>
>
> On 28/09/2017 13:46, Peng Xiao wrote:
>
> even with CL=QUORUM,there is no guarantee to be sure to read the same data
> in DC2,right?
> then multi DCs looks make no sense?
>
>
> ------------------ 原始邮件 ------------------
> *发件人:* "DuyHai Doan";<do...@gmail.com> <do...@gmail.com>;
> *发送时间:* 2017年9月28日(星期四) 下午5:45
> *收件人:* "user"<us...@cassandra.apache.org> <us...@cassandra.apache.org>;
> *主题:* Re: data loss in different DC
>
> If you're writing into DC1 with CL = LOCAL_xxx, there is no guarantee to
> be sure to read the same data in DC2. Only repair will help you
>
> On Thu, Sep 28, 2017 at 11:41 AM, Peng Xiao <25...@qq.com> wrote:
>
>> Dear All,
>>
>> We have a cluster with one DC1:RF=3,another DC DC2:RF=1 only for ETL,but
>> we found that sometimes we can query records in DC1,while not able not find
>> the same record in DC2 with local_quorum.How it happens?
>> Could anyone please advise?
>> looks we can only run repair to fix it.
>>
>> Thanks,
>> Peng Xiao
>>
>
>
>
Re: 回复： data loss in different DC
Posted by Reynald Bourtembourg <re...@esrf.fr>.
Hi,
You can write with CL=EACH_QUORUM and read with CL=LOCAL_QUORUM to get
strong consistency.
Kind regards,
Reynald
On 28/09/2017 13:46, Peng Xiao wrote:
> even with CL=QUORUM,there is no guarantee to be sure to read the same
> data in DC2,right?
> then multi DCs looks make no sense?
>
>
> ------------------ 原始邮件 ------------------
> *发件人:* "DuyHai Doan";<do...@gmail.com>;
> *发送时间:* 2017年9月28日(星期四) 下午5:45
> *收件人:* "user"<us...@cassandra.apache.org>;
> *主题:* Re: data loss in different DC
>
> If you're writing into DC1 with CL = LOCAL_xxx, there is no guarantee
> to be sure to read the same data in DC2. Only repair will help you
>
> On Thu, Sep 28, 2017 at 11:41 AM, Peng Xiao <2535053@qq.com
> <ma...@qq.com>> wrote:
>
> Dear All,
>
> We have a cluster with one DC1:RF=3,another DC DC2:RF=1 only for
> ETL,but we found that sometimes we can query records in DC1,while
> not able not find the same record in DC2 with local_quorum.How it
> happens?
> Could anyone please advise?
> looks we can only run repair to fix it.
>
> Thanks,
> Peng Xiao
>
>