清理了86%的space_placeholder_file文件，然后执行了config set low-space-ratio 0.85后，剩下的15个region很快就迁移完了 
/dev/sdb 3.7T 625G 3.1T 17% /work
/dev/dfa 3.0T 2.2T 746G 75% /work
/dev/nvme0n1 3.5T 2.2T 1.4T 62% /work
/dev/nvme0n1 7.0T 5.7T 1.4T 81% /work
/dev/nvme0n1 7.0T 5.7T 1.4T 81% /work
/dev/nvme0n1 7.0T 5.7T 1.4T 81% /work