sized of infrastructure for Redis Cluster

[Eduardo Diaz]

Hi!

I need help for estimate size of Redis Cluster for 48 millions of register in memory, it's for cache purpose and I think have 2 master with 3 slaves i.e master1 with slave1 and master 2 with 2 slaves.

Regards :)

[AlexanderB]

Hey Eduardo. 

I'm not exactly sure what you're asking. 

The best way to do an estimate though, would be to build a quick prototype that adds a few thousand fake entries and the using the Redis Info commands to see how much memory that takes. Using that as a baseline, you can do some math to figure out how much Ram you'd need for 48 million entries. It really depends on how big each entry is, which varies drastically between projects. 

The other issue you'll run into, is that Redis cluster is built to work with a minimum of 6 nodes, 3 masters and 3 slaves. Setting those up so that you have 1 master and 1 slave per host works fine, but you need masters on at least 3 separate hosts, and the slave for any given master should be on a different host. You need at least 3 masters for a cluster. Masters monitor each other and build consensus on which nodes appear to be down. If you only have 2 masters, and try and set the threshold for consensus at 1, any minor connection error between the two masters will cause both of them to think the other is down. Having 3 masters means that at least 2 need to agree that the third is down.