I’m wiping some drives for a friend. 120GB drive is first up. My machine is 8 core Xeon, 32GB ram.
dd if=/dev/random of=/path/to/disk/im/wiping bs=4M status=progress
The first time it ran 5MB/s. I let it run overnight and it was finished in the morning, about 8 hours. I woke up, ran the command exactly as before . It was chugging along at 5MB/s when I left for work. When I get home, I find it has dropped to 2MB/s and about half the progress that I was expecting to see was completed. It has now dropped to 1.9MB/s and is 14.5 hours after I started the second round. Why would my throughput drop by over half on the second run?