I've noticed that having torrented files (OS images, etc) download directly to the storage zpool can really slow down reads from the pool. Pausing the download software during sustained read events temporarily resolves the issue, but isn't really something I can do regularly.
I have a spare SSD...
Something like the opposite on FreeBSD. The second of these two bug reports:
258573 – www/chromium Could not install package: 'FAILED_TO_COPY_EXTENSION_FILE_TO_TEMP_DIRECTORY'
258679 – www/chromium: Unable to download files with chromium-92.0.4515.159_2