Re: Does LOCAL_ONE still replicate data?

[shalom sagges]

 It's advisable to set the RF to 3 regardless of the consistency level.

If using RF=1, Read CL=LOCAL_ONE and a node goes down in the local DC, you
will not be able to read data related to this node until it goes back up.
For writes and CL=LOCAL_ONE, the write will fail (if it falls on the token
ranges of the downed node).



On Tue, May 8, 2018 at 3:05 PM, Lucas Benevides  wrote:

> Yes, but remind that there is Write Consistency and Read Consistency.
> To prevent the reads from reaching the other DC, you should set the Read
> Consistency LOCAL_ONE.
> As Hannu Kroger said, the LOCAL_ONE may be enough to you but maybe not if
> you want to be sure that your data was written also in another DC.
>
> Lucas B. Dias
>
>
> 2018-05-08 7:26 GMT-03:00 Hannu Kröger :
>
>> Writes are always replicated to all nodes (if they are online).
>>
>> LOCAL_ONE in writes just means that client will get an “OK” for the write
>> only after at least node in local datacenter has acknowledged that the
>> write is done.
>>
>> If all local replicas are offline, then the write will fail even if it
>> gets written in your other DC.
>>
>> Hannu
>>
>>
>> On 8 May 2018, at 13:24, Jakub Lida  wrote:
>>
>> Hi,
>>
>> I want to add a new DC to an existing cluster (RF=1 per DC).
>> Will setting consistency to LOCAL_ONE on all machines make it still
>> replicate write requests sent to online DCs to all DCs (including the new
>> one being rebuilt) and only isolate read requests from reaching the new DC?
>> That is basically want I want to accomplish.
>>
>> Thanks in advance, Jakub
>>
>>
>>
>

Re: Does LOCAL_ONE still replicate data?

[Lucas Benevides]

Yes, but remind that there is Write Consistency and Read Consistency.
To prevent the reads from reaching the other DC, you should set the Read
Consistency LOCAL_ONE.
As Hannu Kroger said, the LOCAL_ONE may be enough to you but maybe not if
you want to be sure that your data was written also in another DC.

Lucas B. Dias


2018-05-08 7:26 GMT-03:00 Hannu Kröger :

> Writes are always replicated to all nodes (if they are online).
>
> LOCAL_ONE in writes just means that client will get an “OK” for the write
> only after at least node in local datacenter has acknowledged that the
> write is done.
>
> If all local replicas are offline, then the write will fail even if it
> gets written in your other DC.
>
> Hannu
>
>
> On 8 May 2018, at 13:24, Jakub Lida  wrote:
>
> Hi,
>
> I want to add a new DC to an existing cluster (RF=1 per DC).
> Will setting consistency to LOCAL_ONE on all machines make it still
> replicate write requests sent to online DCs to all DCs (including the new
> one being rebuilt) and only isolate read requests from reaching the new DC?
> That is basically want I want to accomplish.
>
> Thanks in advance, Jakub
>
>
>

Re: Does LOCAL_ONE still replicate data?

[Hannu Kröger]

Writes are always replicated to all nodes (if they are online).

LOCAL_ONE in writes just means that client will get an “OK” for the write only 
after at least node in local datacenter has acknowledged that the write is done.

If all local replicas are offline, then the write will fail even if it gets 
written in your other DC.

Hannu

> On 8 May 2018, at 13:24, Jakub Lida  wrote:
> 
> Hi,
> 
> I want to add a new DC to an existing cluster (RF=1 per DC).
> Will setting consistency to LOCAL_ONE on all machines make it still replicate 
> write requests sent to online DCs to all DCs (including the new one being 
> rebuilt) and only isolate read requests from reaching the new DC? That is 
> basically want I want to accomplish.
> 
> Thanks in advance, Jakub

Does LOCAL_ONE still replicate data?

[Jakub Lida]

Hi,

I want to add a new DC to an existing cluster (RF=1 per DC).
Will setting consistency to LOCAL_ONE on all machines make it still
replicate write requests sent to online DCs to all DCs (including the new
one being rebuilt) and only isolate read requests from reaching the new DC?
That is basically want I want to accomplish.

Thanks in advance, Jakub