Wed Oct 19 18:45:47 2011
Last write time: Wed Oct 19 18:45:47 2011
Mount count: 1
Maximum mount count: 20
Last checked: Wed Oct 19 18:35:36 2011
Check interval: 0 (<none>)
Lifetime writes: 2511 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: ea117174-a04a-412e-a067-7972804f83d7
Journal backup: inode blocks
Setting properties works as well:
[root@localhost sbin]# tune2fs -L test /dev/iscsi/test
tune2fs 1.42-WIP (02-Jul-2011)
[root@localhost sbin]# tune2fs -l /dev/iscsi/test | head -10
tune2fs 1.42-WIP (02-Jul-2011)
Filesystem volume name: test
Last mounted on: /mnt/mnt
[...]
e4defrag
e4defrag is a new tool to defragment the ext4 file system. According to the man page:
e4defrag reduces fragmentation of extent based file. The file targeted by e4defrag is created on ext4 filesystem made with “-O extent” option (see mke2fs(8)). The targeted file gets more contiguous blocks and improves the file access speed.
I am not yet sure how this affects file systems used for oracle datafiles. All i can say is that e4defrag seems to work with >16 TB file systems:
[root@localhost sbin]# e4defrag /mnt/
ext4 defragmentation for directory(/mnt/)
[....]
Success: [ 4772040/5065465 ]
Failure: [ 293425/5065465 ]
The failures are from directories which cannot be defragmented.
Conclusion
With the most recent e2fstools (1.42-WIP) it is possible to create ext4 file system larger than 16 TB.
If you do so remember the following:
- the tool is still in development – use at your own risk!
- tune the values for autocheck (after x mounts / after y days)
- adjust the “-i” switch which defnes the bytes/inode ratio; in the example above one inode is created for every 8 MB
- the more inodes you create the longer fsck takes and the more memory it needs
- Resizing the file