Hi Ivan,

> Swap is legacy lightweight version of Ignite Native Persistence. In swap
> mode, we fully rely on OS in storing offheap memory into memory-mapped
> file. We don't provide durability guarantees in this mode. From my point of
> view, after 2.1 release there's no reason to prefer swap mode over Ignite
> Native Persistence.
> Igniters, please correct me if there are still any actual cases.


There is a business use case for the swap space I've come across with
recently. Some applications want to store data entirely in RAM avoiding any
persistence in general (Ignite persistence or 3rd party DB). It's ok for
them to lose a data set in case of a cluster shutdown. However, they want
to avoid OOM exception that might happen if they don't scale out the
cluster in time. And here is the swap space comes to rescue. If a node is
running out of RAM, the OS begins the swap-out/in the process putting off
OOM and DevOps will have much more time to scale the cluster and rebalance
the data.

Right now we indeed can configure both Ignite Native Persistence and
> swapping, but this makes even less sense. Node will just perform extra job
> by persisting data twice.


Guess, that's the point Prachi tried to point out. Could we throw an
exception if a user tries to configure both? As we agreed, it's error-prone
and doesn't make sense in general.

--
Denis

On Fri, Mar 2, 2018 at 1:28 AM, Ivan Rakov <ivan.glu...@gmail.com> wrote:

> Prachi,
>
> Swap is legacy lightweight version of Ignite Native Persistence. In swap
> mode, we fully rely on OS in storing offheap memory into memory-mapped
> file. We don't provide durability guarantees in this mode. From my point of
> view, after 2.1 release there's no reason to prefer swap mode over Ignite
> Native Persistence.
> Igniters, please correct me if there are still any actual cases.
>
> Right now we indeed can configure both Ignite Native Persistence and
> swapping, but this makes even less sense. Node will just perform extra job
> by persisting data twice.
>
> Best Regards,
> Ivan Rakov
>
>
> On 02.03.2018 7:20, Prachi Garg wrote:
>
>> Engineers,
>>
>> How does persistence and swap work when both are enabled? I was under the
>> impression that for a data region you can either have swap or persistence
>> configured at a time, but not both. Please clarify.
>>
>> Thanks,
>> -Prachi
>>
>>
>

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