Date: Sat, 26 Jun 2010 09:17:08 +1000 From: Peter Jeremy <peterjeremy@acm.org> To: freebsd-fs@freebsd.org Subject: mdconfig on ZFS leaks disk space Message-ID: <20100625231708.GB29793@server.vk2pj.dyndns.org>
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I recently did a quick experiment to create an 8TB UFS filesystem
via mdconfig and after destroying the md and deleting the file,
the disk space used by the md was not returned - even after a
reboot. Has anyone else seen this?
I was using a 8.1-prelease/amd64 with everything on ZFS v14 and did:
# truncate -s 8T /tmp/space
# mdconfig -a -t vnode -f /tmp/space
# newfs /dev/md0
/dev/md0: 8388608.0MB (17179869184 sectors) block size 16384, fragment size=
2048
using 45661 cylinder groups of 183.72MB, 11758 blks, 23552 inodes.
This occupied ~450MB on /tmp which uses lzjb compression.
# fsck -t ufs /dev/md0
needed ~550MB VSZ and had ~530MB resident by the end.
# mount /dev/md0 /mnt
# df -k /mnt
/dev/md0 8319620678 4 7654051020 0% 2 1075407868 0% /mnt
I then copied a random collection of files into /mnt, boosting the
size of /tmp/space to ~880MB.
# umount /mnt
# fsck -t ufs /dev/md0
# mdconfig -d -u 0
# rm /tmp/space
At this point, 'df' on /tmp reported 881MB used whilst 'du' on /tmp
report 1MB used. lsof showed no references to the space. Whilst
there were snapshots of /tmp, none had been taken since /tmp/space
was created. I deleted them anyway to no effect.
Rebooting the system had no effect.
I eventually recovered the space by doing a "zfs destroy zroot/tmp"
and re-creating it. This showed the in the pool increased by exactly
the amount of extraneous space.
--=20
Peter Jeremy
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