I was pretty impressed by this:

ChatGPT 3.5

User:
if you’re going to use dd to write random data over a hard drive device what block size is best?

ChatGPT:
When using the dd command to write random data over a hard drive device, the choice of block size can impact the performance of the operation. The optimal block size can vary depending on the specific circumstances, but there are some general guidelines you can follow.

A common recommendation is to use a block size that is a multiple of 4 KB (4096 bytes), which is often the physical sector size of modern hard drives. This alignment can improve performance because it matches the underlying hardware.

Here’s an example of using dd with a block size of 4 KB:

$ dd if=/dev/urandom of=/dev/sdX bs=4K

Replace /dev/sdX with the actual device name you want to overwrite, and adjust the block size (bs) according to your needs.

However, keep in mind that there is no one-size-fits-all answer, and performance may vary depending on your specific hardware and use case. You might want to experiment with different block sizes to see what works best for your situation.

Additionally, when overwriting a hard drive for security reasons (e.g., before decommissioning or selling it), consider using tools specifically designed for secure erasure, such as shred or wipe. These tools often implement more sophisticated algorithms to ensure data is thoroughly and securely overwritten.