BZ2-ing up a terabyte of zeroes (back when a TB was more than people commonly had, then zipping that file up together with another file, to bypass virus scanners in emails that prevent emailing .exe files.
I’ve also seen a self-referential .zip file somewhere that contains itself.
It didn’t, but due to unrelated reasons. The root FS was mounted r/w, so the regular IO eventually overwhelmed the network’s ability to copy stuff.
But no worries, a reboot later, with unmounted FS, I finished the same thing.
Copying the disk of a running system appears to be fine in LVM. Copying is done block-by-block, and the only thing it has to do to make it atomic is: in case of a conflict (writing into a block that’s being copied right now), postpone writing to a block until it’s copied, then finish the write in the new location. Or else, abort the copy, finish the write, then copy again.