Why does the btrfs file system report low space, but the system monitor shows free 15 gigabytes?

Question

linux

Then, I tried defragmentation, balancing, and even fstrim (I have an SSD). In addition, the write speed suffers terribly, the speed on the SSD is 1-3 mb / s, the read speed is 90 mb / s (testing was carried out with synchronous mode and disabled cache (repeat reading gives 300 mb / s)).

Answer 1

Stop eating cactus, put ext4 and don't suffer, hosspade.

Answer 2

The btrfs filesystem works on the principle of Copy on Write, so it needs a certain amount of free space for normal and correct operation. In addition, the SSD itself must be left with a good piece of free unallocated disk space - over provisional.
Read about the requirements for this FS for normal operation.

Answer 3

You need to balance the file system tree.
https://btrfs.wiki.kernel.org/index.php/Manpage/bt...