ext3 vs ext4 - mesmo tamanho de disco, menos espaço em disco utilizável sob ext4 comparando com ext3. porque?

Question

Os arquivos copiados do sistema de arquivos ext3 não se encaixam no sistema de arquivos ext4 do mesmo tamanho.

Como reproduzir:

crie dois arquivos de 1 GB,

dispositivo de loop de configuração para cada,

crie um sistema de arquivos, um ext3, um ext4,

montar,

arquivos rsync de / usr / lib para a pasta ext3 até ficarem completos,

tente rsync arquivos da pasta ext3 para o ext4, mas isso falha devido ao espaço em disco.

Eu esperaria que todos os arquivos da pasta ext3 se encaixem na pasta ext4

(veja log, o próximo arquivo a ser copiado é maior que o espaço disponível e ainda resta mais alguns arquivos para copiar)

Alguém pode explicar por quê? ou melhor o que fazer para obter o mesmo ou mais espaço em disco usando o ext4?

este é o sistema debian8

root@blackoil:~#  uname -a
Linux blackoil 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt7-1 (2015-03-01) x86_64 GNU/Linux


root@blackoil:~# dd if=/dev/zero of=e3fs bs=1M count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 6.07722 s, 173 MB/s


root@blackoil:~# dd if=/dev/zero of=e4fs bs=1M count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 6.21495 s, 169 MB/s



root@blackoil:~# losetup /dev/loop3 e3fs
root@blackoil:~# losetup /dev/loop4 e4fs
root@blackoil:~# mkfs.ext3 -m 0 /dev/loop3



mke2fs 1.42.12 (29-Aug-2014)
Discarding device blocks: done                            
Creating filesystem with 256000 4k blocks and 64000 inodes
Filesystem UUID: 8871cd27-5c82-4fa9-acaa-11c2ca200d08
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done



root@blackoil:~# mkfs.ext4 /dev/loop4
mke2fs 1.42.12 (29-Aug-2014)
Discarding device blocks: done                            
Creating filesystem with 256000 4k blocks and 64000 inodes
Filesystem UUID: 71b69de9-0858-4189-8e1f-907efd61f51d
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done



root@blackoil:~# mkdir -p /mnt/e3
root@blackoil:~# mkdir -p /mnt/e4



root@blackoil:~# dumpe2fs /dev/loop3
dumpe2fs 1.42.12 (29-Aug-2014)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          8871cd27-5c82-4fa9-acaa-11c2ca200d08
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype sparse_super large_file
Filesystem flags:         signed_directory_hash 
Default mount options:    user_xattr acl
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              64000
Block count:              256000
Reserved block count:     0
Free blocks:              247557
Free inodes:              63989
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      62
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         8000
Inode blocks per group:   500
Filesystem created:       Mon Jul 20 15:21:53 2015
Last mount time:          n/a
Last write time:          Mon Jul 20 15:21:53 2015
Mount count:              0
Maximum mount count:      -1
Last checked:             Mon Jul 20 15:21:53 2015
Check interval:           0 (<none>)
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               256
Required extra isize:     28
Desired extra isize:      28
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      a35b09fe-b755-49b6-a94d-eb8f2960e5a6
Journal backup:           inode blocks
Journal features:         (none)
Journal size:             16M
Journal length:           4096
Journal sequence:         0x00000001
Journal start:            0



root@blackoil:~# dumpe2fs /dev/loop4
dumpe2fs 1.42.12 (29-Aug-2014)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          71b69de9-0858-4189-8e1f-907efd61f51d
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags:         signed_directory_hash 
Default mount options:    user_xattr acl
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              64000
Block count:              256000
Reserved block count:     12800
Free blocks:              247562
Free inodes:              63989
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      62
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         8000
Inode blocks per group:   500
Flex block group size:    16
Filesystem created:       Mon Jul 20 15:22:16 2015
Last mount time:          n/a
Last write time:          Mon Jul 20 15:22:16 2015
Mount count:              0
Maximum mount count:      -1
Last checked:             Mon Jul 20 15:22:16 2015
Check interval:           0 (<none>)
Lifetime writes:          16 MB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               256
Required extra isize:     28
Desired extra isize:      28
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      33846c93-9d1a-4117-a7c8-1566e96e8e73
Journal backup:           inode blocks
Journal features:         (none)
Journal size:             16M
Journal length:           4096
Journal sequence:         0x00000001
Journal start:            0




root@blackoil:~# mount /dev/loop3 /mnt/e3
root@blackoil:~# mount /dev/loop4 /mnt/e4


root@blackoil:~# rsync -a /usr/lib /mnt/e3
rsync: recv_generator: mkdir "/mnt/e3/lib/python2.6/xml/sax" failed: No space left on device (28)
*** Skipping any contents from this failed directory ***
rsync: write failed on "/mnt/e3/lib/python2.6/httplib.py": No space left on device (28)
rsync error: error in file IO (code 11) at receiver.c(393) [receiver=3.1.1]


root@blackoil:~# df |grep '/mnt/e'
/dev/loop3            991512    991512         0 100% /mnt/e3
/dev/loop4            991512      1264    922664   1% /mnt/e4

root@blackoil:~# cd /mnt/e3

root@blackoil:/mnt/e3# rsync -a . /mnt/e4
rsync: write failed on "/mnt/e4/lib/pepperflashplugin-nonfree/libpepflashplayer.so": No space left on device (28)
rsync error: error in file IO (code 11) at receiver.c(393) [receiver=3.1.1]

root@blackoil:/mnt/e3# df | grep '/mnt/e'
/dev/loop3            991512    991512         0 100% /mnt/e3
/dev/loop4            991512    959372         0 100% /mnt/e4
root@blackoil:/mnt/e3# df -i | grep '/mnt/e'
/dev/loop3            64000    8939    55061   14% /mnt/e3
/dev/loop4            64000    8531    55469   14% /mnt/e4

root@blackoil:/mnt/e3# rsync -av . /mnt/e4
sending incremental file list
lib/pepperflashplugin-nonfree/
lib/pepperflashplugin-nonfree/libpepflashplayer.so
lib/pepperflashplugin-nonfree/manifest.json
lib/pepperflashplugin-nonfree/pubkey-google.txt
lib/pkgconfig/dbus-python.pc
lib/pkgconfig/geoclue-2.0.pc
lib/pkgconfig/gnome-system-tools.pc
lib/pkgconfig/keybinder.pc
lib/pkgconfig/libgdiplus.pc
lib/pkgconfig/libquvi-scripts.pc
lib/pkgconfig/libwnck-1.0.pc
lib/pkgconfig/libxfce4menu-0.1.pc
lib/pkgconfig/libxklavier.pc
lib/pkgconfig/notify-python.pc
lib/pkgconfig/pm-utils.pc
lib/pkgconfig/tomboy-addins.pc
lib/pkgconfig/unique-1.0.pc
lib/pkgconfig/xkbcomp.pc
lib/pkgconfig/xorg-wacom.pc
lib/pm-utils/

( ......   some removed due to 30000 lines limit posting question)

rsync: write failed on "/mnt/e4/lib/pepperflashplugin-nonfree/libpepflashplayer.so": No space left on device (28)
rsync error: error in file IO (code 11) at receiver.c(393) [receiver=3.1.1]

root@blackoil:/mnt/e3# df |grep 'mnt/e'
/dev/loop3            991512    991512         0 100% /mnt/e3
/dev/loop4            991512    959372         0 100% /mnt/e4

root@blackoil:/mnt/e3# ls -l /mnt/e4/lib/pepperflashplugin-nonfree/libpepflashplayer.so
ls: cannot access /mnt/e4/lib/pepperflashplugin-nonfree
/libpepflashplayer.so: No such file or directory


root@blackoil:/mnt/e3# ls -l lib/pepperflashplugin-nonfree/libpepflashplayer.so
-rw-r--r-- 1 root root 17370752 Mar 14 09:08 lib/pepperflashplugin-nonfree/libpepflashplayer.so


root@blackoil:/mnt/e3# mount |grep 'mnt/e'
/dev/loop3 on /mnt/e3 type ext3 (rw,relatime,data=ordered)
/dev/loop4 on /mnt/e4 type ext4 (rw,relatime,data=ordered)

    

Answer 1

Está na sua contagem de blocos de reserva:

ext3: Contagem em bloco: 256000 Contagem de blocos reservados: 0

ext4: Contagem em bloco: 256000 Contagem de blocos reservados: 12800

a correção: # tune2fs -m 0 e4fs