Does it do this for anything else? If you run low on RAM it could be using disk swap space as RAM so check if you system has enough RAM.

There is at least a terabyte of free disk space and 32G of ram. Only 5% of ram is being used. This only happens on youtube. I am sure it is the caching of the youtube feed.

Is it a HDD or SSD or NVMe drive? Can you give specs of your Hardware?

Disk is a HGST 3TB Sata 6.0. Not SSD. I am asuming NVMe is Non-Volitile Memory, and that would be a no. Processor: AMD FX(tm)-8350 Eight-Core Processor × 8 Video: AMD TAHITI (DRM 2.43.0 / 4.4.0-130-generic, LLVM 6.0.0) Running Ubuntu 16.04.4 Xenial 4.4.0-130-generic kernel. Anything else?

Hi, would suspect you are correct on that but to run constantly is something else.

You do not mention CPU %, Ram amount is great.

You have turned off Accessibility Services by putting a Check in the box ? If you can here the disk can you perform any disk checks on it to make sure it is in good condition and if SMART displays any info ?

Can see if not buffering improves anything if have a good connection : https://addons.mozilla.org/firefox/addon/youtube-no-buffer-autoplay/

Ram is 32gb. CPU usage is normal. like 4% max. I do not see any accessibility options in pref... That add on does not seem to be related. The problem feels like it is taking the youtube feed and writing real small pieces of data to the disk cache. So small that it causes it to write tiny pieces at a fast rate to match the rate at which the feed is coming in. Maybe the size of the disk cache commits are very small and therefore the caching must happen many times per second to keep up with the youtube feed.

Since it uses 5% RAM my guess is the O/S as mentioned is doing something else. Is this a clean install of Linux with nothing else added?

This is not a fresh install of Linux , there are many installed applications. What does "it" refer to in the first sentence, and what do you think "doing something else" would be?

I am thinking now it is the firefox -contentproc -childID 1 -isForBrowser...(way to long to insert here) that is listed in the iotop disk usage monitor program. I think the tabs are creating sub-processes that are cahing to disk. These processes may not be under the control of the preferences that firefox is using. I say this because, no matter what I do I can not make the constant disk cahing stop. Without shutting donw firefox. I can not have the disk thrashing constantly.

Hi, ok it's time : please try a Refresh but Note that this does more than uninstalling and re-installing does. Normal uninstalling does not remove some preferences which may have become corrupt. Please Refresh but do this 1st:

• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer
• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

then

• https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings

TEST....... If no issues then Extensions which need to be added back in 1 at a time and tested ..... Or it is your Profile : Make a new one and test ...:

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

If is your Profile :

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Note: Any customization will revert back to default, you will also need to reinstall Extensions.

Please let us know if this solved your issue or if need further assistance.

Already have done that. I am definitely suspecting session store disk caching. Turning it off does not help. Turning the disk caching off does not help either. Session store does not seem to cache to memory when I set it to use memory. I do not see a setting that makes session store use memory instead of disk. I suspect it is hard coded to use a specific file. I also seems like the session store starts automatically when firefox is opened. I set the session store interval to something massive, but it still grinds immediately when I open firefox and view a video. I may have had some success when I started a video and then stopped the video with the pause button , ( and that after a few seconds , the grinding stopped) and then started it again. Seems like it stopped for awhile. Going to do some repeat tests. I can say that the grinding is happening on my linux and windows. Windows seems more kind to the drive than linux is (Quieter).

This is not just for a SSD. I myself do not use sessions so I tripled the recommended time he suggests in the article :

• https://www.servethehome.com/firefox-is-eating-your-ssd-here-is-how-to-fix-it/