- Overview
- Requirements
- Hardware requirements
- Software requirements
- Installation
- Upgrade
Software requirements
Platform |
Supported Versions |
---|---|
RHEL/CentOS 8 |
|
Ubuntu |
Server version is recommended for production installations. Desktop version is only recommended for development deployments. |
The HAA cluster needs three servers for a healthy operation.
Under normal circumstances, the HAA cluster servers have the following roles:
- one principal server – it holds a data shard, and it accepts read and write database operations from the outside world;
- one secondary server – it holds a copy of the data shard;
- one secondary server – it holds no data, it exists for quorum purposes only.
The HAA cluster supports a single server failure only.
- If one of the servers goes down, no matter which one, the HAA cluster continues working, and a warning is shown in the Web
management interface. You can find more information by running the
rlcheck
command, usually found in/opt/redislabs/bin
. You can also append--continue-on-error
to therlcheck
command. - If two servers fail, the HAA cluster fails as well, even if the principal server is still online.
Building an HAA cluster with more than three servers is possible but offers no real benefit.
There is no increase in the number of servers that can fail. In the case of a five-node HAA cluster, if the principal node and the secondary node keeping the data shard copy both fail, the entire cluster fails as well, and there is no data shard reallocation to other nodes.
HAA supports both IPv4 and IPv6. For more details on the support for multi-IP and IPv6, refer to Redis documentation.