[Q] Is this true and does it mean there is dynamicmentation in ext2/3?

Damian Menscher menscher at uiuc.edu
Sat Jun 18 19:36:59 UTC 2005

On Sat, 18 Jun 2005, Theodore Ts'o wrote:
> On Fri, Jun 17, 2005 at 06:28:03PM -0400, Maurice Volaski wrote:
>>> You don't need to defragment ext2/ext3 because as you use the
>>> filesystem file blocks and inodes are moved around and reallocated
>>> to keep the data nearly contiguous. It's not perfect, but it works
>>> fairly well and you should almost never see a performance
>>> degradation caused by the filesystem's fragmentation.
>> Is this statement accurate and does it mean ext2/3 is performing a
>> sort of dynamic defragmentation?
> Ext2/3 has advanced algorithms to make sure that the blocks that are
> allocated avoid fragmentation, but it is not doing any kind of dynamic
> moving of blocks/inodes.

It's probably worth noting that SGI's XFS filesystem has a userland 
program to eliminate fragmentation: fsr (file system reorganizer).  It 
basically works by copying files around, and depending on the underlying 
filesystem to allocate contiguous blocks for the new copies of files. 
It's a neat hack to allow you to defrag a drive without needing too much 
kernel-mode involvement.

Of course, you probably would need some special stuff to ensure inode 
numbers don't change (NFS depends on them for filehandles, etc).

Damian Menscher
-=#| Physics Grad Student & SysAdmin @ U Illinois Urbana-Champaign |#=-
-=#| 488 LLP, 1110 W. Green St, Urbana, IL 61801 Ofc:(217)333-0038 |#=-
-=#| 4602 Beckman, VMIL/MS, Imaging Technology Group:(217)244-3074 |#=-
-=#| <menscher at uiuc.edu> www.uiuc.edu/~menscher/ Fax:(217)333-9819 |#=-
-=#| The above opinions are not necessarily those of my employers. |#=-

More information about the Ext3-users mailing list