I don’t think it’s the controller, it should easily be able to keep up with LBA requests. I agree with AlleyViper, this is most likely a Condicive software glitch. My hypothesis is that something is that some permanent or temporary data array is, under some circumstances, running out of pre-allocated or available space, or possibly some numerical value is exceeding type allowd value (not likely these days).
Two things that can negatively affect caching performance:
Security software scans. We all (hopefully) do a quick scan each boot, and probably idle time scans – and every so often I scan every single file, archive, etc. This makes the cache record lots of LBAs many of which are otherwise rarely read.
Defragging moves data from one LBA to another, cache has to adjust to new read patterns. Active defraggers that try to move files around in real time to keep them contiguous generate ‘spurious’ (from a caching perspective) LBA reads and change which LBAs hold which data, again forcing the cache to reorder/reprioritize.
