I am experiencing a weird behaviour.
I have a huge FileMaker 16 file, 154GB, that FileMaker server struggles to backup.
If I copy this file on a backup disk, it takes 15 hours to complete the copy (SSD to HDD).
If I copy the same file on the same main disk (desktop folder, for example), it takes no time (SSD to itself). The main HD has - 300GB of free space (according to MacOS High Sierra) before the copy. After that copy, it still has 300 GB free.
I make changes to the file, then close the file from FileMaker server and it takes about 2 hours to close and compact the file. But then I copy the file on the desktop folder (in a subfolder), and again, it takes no time. And again, the disk still has 300 GB free!
I repeated this after deleting some millions records, the file shrinked to 141GB. Again, I copied on a folder of the desktop folder, and the free space remains around 300GB.
And so on.
How is that?
If it were a bundle file, I could imagine that the OS copies just the changed parts, and hard-links the ones that are identical, sparing the space. But this is a single FileMaker file, and I can open each version of the file and see that they are different but it seems that all of them take no space at all.
Any idea why this happens? Is it High Sierra's new file system?
If so, why FileMaker doesn't take advantage of it when performing the backups?