In many of our new deployment projects, we face the common question “How much CPU, RAM and disk space does Radiator need for x users?” While conservative estimates can be given, there is much more to this question than a simple figure.
The requirements of the system depend on the use case, backend, and implementation. In this blog post we will go over the variables and why it actually is misleading from us to give an answer to this question - but at the same time, we are always happy to help you with the hardware correct sizing.
Use case
There are major differences between the requirements for different authentication methods. The differences can be divided to two: Number of transactions per authentication, and number of interim-accounting transactions per session. One PEAP or EAP-TTLS request can consist of many messages, while a fixed-line authorisation has less transactions.
In reality, AAA servers are usually not the hold-up. Database latency is often the limit for AAA server performance. The database just does not respond in time when the load is high enough. In networking authentication, some use cases are read-heavy and some write-heavy on the database. To allow for better system performance, the database model should be optimised based on the demand for writes over reads or the other way around. What can and should be done is separate VMs for Radiator and the database. It is always better to run AAA server and database on separate servers.
Implementation
Network design plays an important role in ensuring your Radiator setup is sized sufficiently. Radiator can be configured to run as a loadbalancer for other Radiator instances. While there also are other loadbalancer options, a setup loadbalanced with Radiator loadbalancer configuration has better throughput than one without loadbalancing.
The requirements
In conclusion, there are many factors that affect the system performance, and sizing Radiator depends heavily on the use case and preferred architecture. However, a conservative starting point that we give customers is that each Radiator instance requires 1 vCPU and 0.5 GB RAM and it runs around 1000 TPS. This may heavily vary depending on the use case.
As for disk space, Radiator itself takes around 20 MB of disk space. This does not take into account requirements of the operating system and log data generated by Radiator. However, the Radiator logs can be shipped off to another log host machine to assure the Radiator host’s disk is not filled with log data.
