Distribute maxmemory between databases.

[Vadim Dzyuban]

I setup "maxmemory 3Gb" in redis.conf file. Now I'd like to distribute that 3Gb between 4 databases as follows: db0 - 1Gb, db1 - 0.5Gb, db2 - 0.5Gb, db3 - 1Gb.
Is there any way to do it ?
Thanks in advance.

[Itamar Haber]

Hello Vadim,

Redis' databases are more like different namespaces than actual separate entities. As such, all databases in the same Redis instance share the configuration settings, `maxmemory` included (but also persistence, eviction, and all the rest).

The way to achieve what you're after is to install 4 separate Redis servers - each with its own settings.

Itamar

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[Vadim Dzyuban]

You're right Itamar, that all databases share one config file. But I think databases are treated as separate entities. To prove that I would refer to the redis-cli 'select <db_number>' to switch from one db to another. Also, there is redis-cli command 'migrate key' from one db to another which referenced db as an integer number. That is redis-cli commands refer to the databases as to the entities. I think, it might be more effective to setup multiple config files somehow (not sure how to do it) - one per database, rather than setup multiple redis servers with only one db in each server in my particular use case.
Thank you for the response Itamar.

[Matt Palmer]

On Wed, Jun 15, 2016 at 07:42:40PM -0700, Vadim Dzyuban wrote:
> You're right Itamar, that all databases share one config file. But I think
> databases are treated as separate entities.

No, they're treated as separate namespaces.

> To prove that I would refer to
> the redis-cli 'select <db_number>' to switch from one db to another.

That changes the namespace being acted upon.

> Also, there is redis-cli command 'migrate key' from one db to another
> which referenced db as an integer number.

That is moving a key from one namespace to another.

> That is redis-cli commands
> refer to the databases as to the entities.

Yes, it is referring to the namespace as an entity.

> I think, it might be more
> effective to setup multiple config files somehow (not sure how to do it) -
> one per database

You can't do that. A config file operates on a Redis instance, not on a
single database namespace within that instance.

> rather than setup multiple redis servers with only one
> db in each server in my particular use case.

No, it wouldn't. Setup multiple Redis instances and move on with your day.

- Matt