Correct, we are entirely on ext4 now (there might be one or two old pods running JFS left, I would need to double check).
We figured out a way to work around the 16 TByte volume limit originally, but now ext4 even supports larger volumes so that isn't a problem at all anymore.
More random history: At the time we chose JFS it looked like XFS might lose support (XFS was created by a now defunct company I used to work for called SGI). Well, the world is a strange place and XFS now has more support than JFS, despite SGI going out of business. But in the end, ext4 is the "most commonly used" linux file system and therefore is arguably the most supported with extra tools and such, and the performance of ext4 in many areas seems higher than JFS (at least for our use case) so the decision becomes easier and easier to go with ext4.
