[20170928]tune4fs.txt
--//昨天做了使用tune2fs调整保留块百分比的测试,今天才发现,我们生产分区不是ext3而是ext4.
--//我重复测试看看:
1.建立测试环境:
# dd if=/dev/zero of=100m bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 0.272268 seconds, 385 MB/s
--//注:bs=1M,M要大写.另外注意输出的MB的单位,感觉这样输出不对.
# mkfs.ext4 100m
mke4fs 1.41.12 (17-May-2010)
100m is not a block special device.
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
25688 inodes, 102400 blocks
5120 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67371008
13 block groups
8192 blocks per group, 8192 fragments per group
1976 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 20 mounts or
180 days, whichever comes first. Use tune4fs -c or -i to override.
# tune2fs -l 100m
tune2fs 1.39 (29-May-2006)
tune2fs: Filesystem has unsupported feature(s) while trying to open 100m
Couldn't find valid filesystem superblock.
--//无法获取信息.
# tune4fs -l 100m
tune4fs 1.41.12 (17-May-2010)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 1b697663-dd42-4290-88cb-df3face16aba
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: (none)
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 25688
Block count: 102400
Reserved block count: 5120
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Free blocks: 93504
Free inodes: 25677
First block: 1
Block size: 1024
Fragment size: 1024
Reserved GDT blocks: 256
Blocks per group: 8192
Fragments per group: 8192
Inodes per group: 1976
Inode blocks per group: 247
Flex block group size: 16
Filesystem created: Wed Sep 27 09:10:38 2017
Last mount time: n/a
Last write time: Wed Sep 27 09:10:38 2017
Mount count: 0
Maximum mount count: 20
Last checked: Wed Sep 27 09:10:38 2017
Check interval: 15552000 (6 months)
Next check after: Mon Mar 26 09:10:38 2018
Lifetime writes: 7678 kB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 128
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: c9d363f1-2cc6-4f9f-8d91-3a407bae5b86
Journal backup: inode blocks
2.测试:
# mount -o loop 100m /mnt/backup/
# df | egrep "backup|File"
Filesystem Size Used Avail Use% Mounted on
/home/oracle/100m 97M 5.6M 87M 7% /mnt/backup
# mkdir /mnt/backup/test
# chown oracle:oinstall /mnt/backup/test
# chmod 777 /mnt/backup/test
--//以oracle用户执行:
$ dd if=/dev/zero of=/mnt/backup/test/96m bs=1M count=96
dd: writing `/mnt/backup/test/96m': No space left on device
87+0 records in
86+0 records out
90357760 bytes (90 MB) copied, 0.554884 seconds, 163 MB/s
# tune4fs -r 0 100m
tune4fs 1.41.12 (17-May-2010)
Setting reserved blocks count to 0
$ rm /mnt/backup/test/96m
$ dd if=/dev/zero of=/mnt/backup/test/96m bs=1M count=96
dd: writing `/mnt/backup/test/96m': No space left on device
87+0 records in
86+0 records out
90357760 bytes (90 MB) copied, 0.521343 seconds, 173 MB/s
# umount /mnt/backup/
# tune4fs -l 100m | grep "Reserved block count:"
Reserved block count: 5120
--//可以发现修改无效!!
# tune4fs -r 0 100m
tune4fs 1.41.12 (17-May-2010)
Setting reserved blocks count to 0
# mount -o loop 100m /mnt/backup/
# df | egrep "backup|File"
Filesystem Size Used Avail Use% Mounted on
/home/oracle/100m 97M 92M 5.2M 95% /mnt/backup
$ dd if=/dev/zero of=/mnt/backup/test/96m bs=1M count=96
dd: writing `/mnt/backup/test/96m': No space left on device
92+0 records in
91+0 records out
95600640 bytes (96 MB) copied, 0.501282 seconds, 191 MB/s
--//对比前面可以写入更多内容.一样注意要在umount状态下修改才有效.
