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A comment on Ions: Develop cloud applications by deploying to a running Datomic cluster. Parent comment

Re:Ions: Develop cloud applications by deploying to a runnin... by alter_eco123 on Thursday June 07, 2018 @10:37AM (#17256095)
> Each layer of this cache provides a different value

What does that mean?

And what kind of actual memory usage should people expect with a "big" database?

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Re:Ions: Develop cloud applications by deploying to a runnin... by stuarthalloway on Thursday June 07, 2018 @01:46PM (#17258271)
Hm, I should have said "value proposition", e.g. SSDs are low latency but can fail, S3 is high latency but "never" fails, etc.

Datomic is designed for data sets larger than memory, and also to do a good job caching working sets that do fit in memory.

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Re:Ions: Develop cloud applications by deploying to a runnin... by alter_eco123 on Friday June 08, 2018 @08:26AM (#17264615)
> Datomic is designed for data sets larger than memory

Of course. But you didn't answer my question.

Let's say someone has an application with 100GB of data in Datomic.

What kind of memory usage should he expect for the "peer" process?

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Re:Ions: Develop cloud applications by deploying to a runnin... by stuarthalloway on Friday June 08, 2018 @08:54AM (#17264785)
That depends on what queries the peer runs. In both On-Prem and Cloud, Datomic maintains an in-memory LRU object cache. Also, you can send queries with different working sets to different processes without having to shard data on ingest. For example, some peers might handle queries related to user transactions while other peers handle analytic or batch work.

See also https://docs.datomic.com/cloud/operation/caching.html.

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