Where can free space on the HDD go?

Question

linux

Good afternoon!
There is a remote server with raid 1 (ext3) on debian
If you look at the directories, then
du / -h --max-dept=1
763G /
And if df -h
/dev/disk/by-uuid/ 1.8T 1.6T 145G 92 % /
A discrepancy of about 800 gigabytes.
Please tell me that I did not take into account how to look more.

Answer 1

ncdu /look again.
The place goes nowhere when the disk crashes and some sectors are marked by the system as bad.

Answer 2

uptime big? Have the files been deleted? The fact is that in linux, unlike windows, the file name and its inode are separate entities, and if you delete an open file, it seems to disappear from the FS, but the space will not be freed until the process closes it.

Answer 3

lsof | grep deleted says anything?
Another option is that you have nginx cached something for 800 gigs (these files do not get into du). Well, or someone else, except for nginx.

Answer 4

сделайте лучше
cd /
du -s * | sort -n

Answer 5

В /var/log случайно вакханалия не творится?

Answer 6

Попробуйте ключ запустить du с ключом --apparent-size и без него:

sudo du -xsh --apparent-size /
sudo du -xsh /

Ещё посмотрите какой процент блоков зарезервирован для root:

$ sudo dumpe2fs -h /dev/sda1 | grep -i "block count"
Block count:              7323904
Reserved block count:     366195
$ calc 366195/7323904
  ~0.04999997269215980985

"lsof | grep deleted" - тоже хороший совет уже упомянутый выше