直接备份数据(以防万一)后把文件系统 convert ( 
https://wiki.archlinux.org/title/Btrfs#Ext3/4_to_Btrfs_conversion )过来就行,再启用 zstd 压缩就好了,一般能压缩的 zstd 压缩结果在 38% 左右,的确很节省空间并延长 SSD 寿命。
我使用的压缩 zstd=3 默认水平,压缩效果分 / 和 /home:
sudo compsize -x /
Processed 514750 files, 311074 regular extents (323117 refs), 295598 inline.
Type       Perc     Disk Usage   Uncompressed Referenced  
TOTAL       58%       14G          24G          25G       
none       100%      8.0G         8.0G         7.8G       
zstd        35%      5.3G          15G          16G       
prealloc   100%      818M         818M        1016M       
sudo compsize -x /home
Processed 4067717 files, 3248206 regular extents (3374612 refs), 2410852 inline.
Type       Perc     Disk Usage   Uncompressed Referenced  
TOTAL       76%      458G         601G         623G       
none       100%      386G         386G         396G       
zstd        33%       71G         214G         226G       
prealloc   100%       37M          37M         144M