I try to avoid Norton whenever possible, so can't say one way or the other for it.
When you get new data for a site, or it updates cookies, whether it writes a lone file for each (like IE), or saves to a more efficient DB (like FF or Chrome), it has to commit it to disk within some deadline.
If it has to write 500 bytes of new data, like a new CSS file, or whatever else, there's 4K to write. Likewise, if it needs to read that cached data back, it has to read that 4K. It can be made more efficient with shared DBs, than flat files, but the end result is the same. If it's not in RAM, yet, it has to go to the disk to get it.
You can see some of this, though not directly the disk activity part*, live. Open the developer tools, and go to the network tab. Experiment with cache on and off. Check the file sizes.
* That can be done, too, but you'll need a different set of tools, and figuring out WTH is going on is more involved.