Hi,
I suspect this being a FAQ already, but I could not find[0] it:
does ext4 really use 5% of available space for internal housekeeping?
After formatting and mounting a ~917GB partition I see:
# df -h /mnt/bench/
Filesystem Size Used Avail Use% Mounted on
/dev/sdb1 917G 200M 871G 1% /mnt/bench
The "200 MB used" would seem more sensible, but the difference between
"available" and "size" is really 46 GB. How comes?
Thanks,
Christian.
[0] http://ext4.wiki.kernel.org/index.php/Frequently_Asked_Questions
PS, a few more details how the filesystem got created and mounted:
# /opt/e2fsprogs/sbin/mkfs.ext4 -V
mke2fs 1.41.0 (10-Jul-2008)
Using EXT2FS Library version 1.41.0
# /opt/e2fsprogs/sbin/mkfs.ext4 /dev/sdb1
[...]
# /opt/e2fsprogs/sbin/tune2fs -E test_fs /dev/sdb1
tune2fs 1.41.0 (10-Jul-2008)
Setting test filesystem flag
# /opt/e2fsprogs/sbin/blkid /dev/sdb1
/dev/sdb1: UUID="cb2892a3-e42f-47c1-930b-6adab0cf023f" TYPE="ext4dev"
# /opt/e2fsprogs/sbin/tune2fs -l /dev/sdb1 | egrep 'features|flags'
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash test_filesystem
# mount -t ext4dev /dev/sdb1 /mnt/bench
# dmesg | tail
[35021.126539] kjournald2 starting. Commit interval 5 seconds
[35021.126963] EXT4 FS on sdb1, internal journal
[35021.126963] EXT4-fs: mounted filesystem with ordered data mode.
[35021.126963] EXT4-fs: file extents enabled
[35021.307115] EXT4-fs: mballoc enabled
# grep sdb1 /proc/mounts
/dev/sdb1 /mnt/bench ext4dev rw,barrier=1,noextents,nomballoc,data=ordered 0 0
--
BOFH excuse #398:
Data for intranet got routed through the extranet and landed on the internet.
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