And to be totally, ridiculously pedantic (this is HN after all) mv is a single atomic metadata operation in the filesystem, which will almost certainly go into

And to be totally, ridiculously pedantic (this is HN after all) mv is a single atomic metadata operation in the filesystem, which will almost certainly go into the filesystem log without any wait on i/o. A big rm is going to generate enough metadata churn that the filesystem log will need to be synced to hardware at least once, and then you've got 2 or 3 orders of magnitude more time to wait (per sync).