Exporting Cache extremely slow – expected?

[polyxo]

I am currently exporting a Cache for shared usage. 21000 images. About 4000 of them are PSDs, mostly RAW based photos with minor edits (all saved without composite layer /max compatibility) to save disk space > cuts down file size to about a third.

Is it expected that creating thumbnails for this relatively low number of files takes about an hour?

[Lumigraphics]

I'm surprised that it doesn't take longer.

[polyxo]

Actually, it took longer. But why? I didn't let it create full previews, just 256 / 1024. For my 21.000 files Bridge needed to write about 42.000 thumbnails.

What on earth can take so long in this process in 2022? My machine should be able to write 12 images at a time and could keep thousands of them in memory…