100% disk access and 100% RAM usage for no reason, completely blocking my ability to work

Show-stopping performance issue here! I am completely blocked from being able to work at all. Premiere is currently using 100% disk access and 100%+ memory usage, sitting idle, doing nothing!

In Premiere Pro 2024, I opened a project originally created in v2023. Was prompted to convert the file format. After doing so, disk access on the drive where the video files are stored immediately skyrocketed to 100%. It stayed that way for a very long time. Two hours later, the drive was still being hammered to death. Completely unable to use Premiere at all, it was dead in the water because it couldn't play any files. CPU usage was near zero.

Resource Monitor showed Premiere reading the source footage files. If it was trying to build peaks and caches, it did so with extreme inefficiency.

Even worse, after closing the project, disk access persisted at 100%. Resource Monitor showed the same few source footage files being read. Eventually Premiere got tired I guess, or it felt it had punished the drive enough, and eventually petered out after about five minutes.

Other projects opened normally, there were a few seconds of heavy disk access but then it went back to normal -- zero access when Premiere is idle.

Of course I restarted the Windows 10 PC, but that made no difference.

Updated to 2024.5, re-converted the original v2023 project file, but that made no difference.

Deleted all Media Cache files through Preferences, but that made no difference.

I did notice that projects using footage encoded with Blackmagic MJPEG codec hit the drive a lot harder than projects using footage encoded with NVIDIA NVENC H264. I guess H264 files don't need caches at all?

The problematic project has about 100 source files, TRT 14 hours, all encoded with Blackmagic MJPEG. Totaling about 400GB, which is kind of a lot, I know. It's showing them all as offline while it hammers the hard drive, presumably trying to build caches and peaks. So one might conclude that there's a performance issue with the codec? It's not hardware accelerated. But there was no issue whatsoever when I originally edited this project in Premiere 2023. And again, CPU usage is near zero, so the problem seems to be completely about hard drive access.

Contrast this with another project using the same codec, with only ten files totaling 3GB, TRT 30 minutes. Even after deleting all cache files, the smaller project takes ~15 seconds to load. The larger project does not finish loading even after two hours. The math here doesn't seem to add up. I could imagine that 400GB would take a half hour at most. Not multiple hours.

I did update the Blackmagic Desktop Video software, which includes the MJPEG codec. Not really relevant, though, because Premiere has native support for MJPEG. It just won't load the audio in the AVI files created by Blackmagic unless the Blackmagic codec is installed. Not a concern for me here because I'm not even using that audio. But updating the Blackmagic software made no difference.

Any way you slice it, a project should not take hours to load, even if the source footage is 400GB. I am really not accustomed to this sort of behavior. Sony Vegas never made me wait for hours while it ground my hard drive to dust, no matter how large the source footage folder was. If this is supposed to be speeding up my workflow, I regret to have to say that it is the opposite of that. It has completely shut me down.

I really don't want to erase my preferences, since it was a huge PITA to get Premiere set up to be even remotely close to an efficient workflow.

So what am I supposed to do here? Reinstall v2023? I doubt that would make any difference, as it seems the issue is just massive inefficiency in building the cache files.

Is there any option to NOT build these cache files? Or to control how many files are read simultaneously? Maybe if it was only reading one file at a time it wouldn't be fighting itself for limited bandwidth?

BTW, the hard drive is not super fast, but it is a 7200 RPM Western Digital platter, internal. Again, if I were to do a backup, I would expect that 400GB would take maybe a half hour to transfer. Not multiple hours!

And why are these caches temporary external files in the first place? If they take so long to build, shouldn't they be persistent? If not stored in the project file, at least stored next to the source footage? That's an option for the peak files. Why not the cache files? Why set things up for failure like this?

In the end, I let the computer sit for hours until the disk access went back to zero. All of the footage in the bins finally read as being found, not pending, and all of the statistics were visible. Tried to access the timeline and BOOM, disk access went back to 100%. What the actual frak?!?! And now RAM usage is pegged at the maximum, too! I have 32GB RAM and have 6GB reserved for other applications. Premiere has gone totally rogue here, consumed 100% of disk time and 100% of memory. Now it's using the page file, completely runaway process, it's currently up to 44 GB and still rising. SITTING IDLE, DOING NOTHING.

I turned off the timeline thumbnails with the super secret hotkey. No change. Disk access still pegged at 100%. RAM usage still greater than the maximum I set aside for Premiere. What is Premiere even doing? It's not building caches, it's not playing the timeline, it's just sitting idle. This is OUTRAGEOUS! Resource Monitor says it's still accessing those source files. But WHY???

How do I get back to being able to actually work?

This is just shocking!!! It's acting like malware!