No space left on disk (PostgreSQL)

I was trying to write a 55GB SQL file to my database. It used to crash each time. I removed logs and did some cleaning to get the server running, but the transaction never used to complete. Latter, I emptied all the tables I was writing into (I had a backup), but even after that, when I tried writing the SQL file, it gave me this error after a series of successful inserts - Could not write to file "pg_subtrans/14C6" at offset 106496: No space left on device. Is there a way out of this? Are there logs related to PGSQL that I should still clean? I've read that moving the pg_xlog might just help? Should I try this? Any help will be appreciated. Thanks! Output of df -h reformatted from comment for readability. Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg_zarkin-lv_root 574G 540G 4.3G 100% / /dev/sda1 194M 35M 150M 19% /boot tmpfs 5.9G 928K 5.9G 1% /dev/shm /dev/mapper/smeidc0-smeisky0 7.2T 5.2T 2.0T 73% /smeidc/sky0 /dev/md0 7.2T 6.5T 400G 95% /smeidc/backup