[redis-db] Can I have 3 Redis Sentinel nodes managing 2 redis nodes?

[Cody R]

I see for failover I need 3 Sentinels to each a quorum, my question is
right now we just have 2 redis servers in a master-slave relationship, Can
I configure sentinel on those 2 + some other random server (since I hear it
doesn't use much resources) and use it for failover between only 2 nodes,
or does it require 3 redis nodes as well?

Thanks!

[h***@gmail.com]

You can certainly have a different number of Sentinels than Redis servers.

Post by Cody R
I see for failover I need 3 Sentinels to each a quorum, my question is
right now we just have 2 redis servers in a master-slave relationship, Can
I configure sentinel on those 2 + some other random server (since I hear it
doesn't use much resources) and use it for failover between only 2 nodes,
or does it require 3 redis nodes as well?
Thanks!

[Abioy Sun]

Yes.
But better read the doc below to be aware of possible issues.

https://redis.io/topics/sentinel#example-3-sentinel-in-the-client-boxes

Post by h***@gmail.com
You can certainly have a different number of Sentinels than Redis servers.

Post by Cody R
I see for failover I need 3 Sentinels to each a quorum, my question is
right now we just have 2 redis servers in a master-slave relationship, Can
I configure sentinel on those 2 + some other random server (since I hear it
doesn't use much resources) and use it for failover between only 2 nodes,
or does it require 3 redis nodes as well?
Thanks!

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[Salvatore Sanfilippo]

To have two Redis instances (master and slave) and three Sentinel
node, is definitely a good setup if you just want a reliable failover.
However something is down or not in a relative way, that is, depending
on where do you observe it. Having three instances with master - slave
- slave with the sentinels in each node has a given set of properties.
Having the Sentinels in the frontends change the properties of the
system. The Sentinel doc is explicit about that, but for normal
failover, your setup is ok.On Thu, Sep 27, 2018 at 8:50 AM Cody R

I see for failover I need 3 Sentinels to each a quorum, my question is right now we just have 2 redis servers in a master-slave relationship, Can I configure sentinel on those 2 + some other random server (since I hear it doesn't use much resources) and use it for failover between only 2 nodes, or does it require 3 redis nodes as well?
Thanks!
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Salvatore 'antirez' Sanfilippo
open source developer - Redis Labs https://redislabs.com

"If a system is to have conceptual integrity, someone must control the
concepts."
— Fred Brooks, "The Mythical Man-Month", 1975.