Finally understood the reason why Samba 4.7.4 wastes huge RAM on NAS4Free 11.1.0.4

I experienced the Samba daemons wolfed a lot of memories when I looked into bad behaviour of CIFS shareing on my friend's NAS. They wastesd gigabyte order memories per one process, then consumed 16GB of physical memory and 64GB of swap. I had no choice but to shut down the machine forcibly. It was clearly unusual. I think the lack of memory caused proximately the problem because ARC couldn't use enough memory and therefore storage performance was poor.

I tried to fiddle with some options, then it seemed a shadow copy option brought the disaster. A following picture shows difference between the option 'On' and 'Off' of top command.

It is alarmingly at-a-glance. The memory usages were different order of magnitude literally. The samba enabled shadow copy option almost dried up the memory in less than a day, on the other hand, disabled one works fine four-day-old alghough the load average is up to 13. FYI, the file sharing service also works in this situation.

The VSS in Samba means a vfs_shadow_copy2 module has some bugs, doesn't it? I felt there were no problem if the options was enabled when NAS4Free was version 9 or 10 although my memory was so dim.