Is here anyone who can help me understand why I have too high disk activity (SSD)? My MacBook Pro 2011 has 8GB of Ram and had maxed specs so it's something related with the software and my system is laggy. I can't make again a clean install.
If a drive is constantly active or your CPU utilization is high (possibly with increased temps and fan speed) when you're not running any apps, check to see if Spotlight is indexing by looking at the Menu Bar icon:
(not indexing)
(indexing)
Launch Activity Monitor and change "My Processes" at the top to "All Processes", then click on the CPU column heading once or twice, so the arrow points downward (highest values on top). Then look to see what may be consuming system resources.