Having had that happen to me I always used some extN and didn't lose any existing files.

Of course that's a decade or more ago and I may be misremembering but a cursory Google looks like other people encountered something like it too.

But, I will say I've had a lot of success using XFS to serve images, particularly tiles. Particularly map tiles that are generated once and then basically static. There it has a lot less overhead when formatted with size=2048, so lots of small files are handled better. Of course, reiserfs was even better, but part of that was with a job I worked on where they just blindly rendered map tiles for the whole earth, and so there were a lot of 50 byte solid blue tiles. Reiser did really well with that, though some deduplication or linking would have been a huge benefit.

I would second this. XFS is great. A few years ago I moved from JFS to XFS for bulk data storage because JFS is pretty abandoned these days. No issues at all with XFS, and never lost any data.

Just make sure it's right for you before you use it (e.g. you cannot shrink XFS volumes as you can ext4)