Thank heaven for sparse files!

We use ImageMagick to do a lot of image processing. I'm not sure what it's up to, but some processing needs to create temporary working files that can be quite large (in /var/tmp by default, I've moved them with TMPDIR because that filled up).

However, I now see this:

/bin/ls -l /storage/tmp
total 203037932
-rw-------   1 user grp       169845176062560 Sep  4 11:18 magick-XXT0aaXE
-rw-------   1 user grp       222497224416 Sep  4 13:24 magick-XXU0aaXE
-rw-------   1 user grp       11499827272024 Sep  4 13:11 magick-XXbFaiKF
-rw-------   1 user grp       15064771904 Sep  4 13:24 magick-XXcFaiKF
-rw-------   1 user grp       18904557170048 Sep  4 10:51 magick-XXtlaGCE
-rw-------   1 user grp       24764978480 Sep  4 13:24 magick-XXulaGCE

or, in more readable units a few seconds later:

/bin/ls -lhs /storage/tmp
total 203038194
33272257 -rw-------   1 user grp          154T Sep  4 11:18 magick-XXT0aaXE
34295031 -rw-------   1 user grp          207G Sep  4 13:24 magick-XXU0aaXE
29432967 -rw-------   1 user grp           10T Sep  4 13:11 magick-XXbFaiKF
9271301 -rw-------   1 user grp           14G Sep  4 13:24 magick-XXcFaiKF
48382483 -rw-------   1 user grp           17T Sep  4 10:51 magick-XXtlaGCE
48384155 -rw-------   1 user grp           23G Sep  4 13:24 magick-XXulaGCE

Ouch. That's on an internal 146G drive.

What on earth is it doing with a 154 terabyte file?