Here’s a brief overview of my FreeNAS/TrueNAS file server.
In 2015, I built a new file server for FreeNAS. Six 1TB Western Digital Red NAS hard drives divided into three mirrored virtual devices (or vdevs). Storage pool was 3TB.

In 2017, I bought a used 3Gbps SAS controller card. In 2020, I replaced all the case fans and added two 2TB Western Digital Red Plus NAS hard drives. Expanded the storage pool from 3TB to 5TB.
In March 2022, I switched from FreeNAS on mirrored 16GB USB drives to TrueNAS on mirrored 120GB SSDs.
In May 2022, after replacing a 1TB hard drive with a 2TB hard drive, I had to replace the failed 120GB SSD.

This year I bought a 6Gbps SAS controller card.