[ale] Ubuntu Linux Defrag EXT4

[Michael Trausch]

On Sat, Sep 11, 2010 at 10:01 PM, Ron Frazier <atllinuxenthinfo at c3energy.com
> wrote:

> I am interested in what everyone thinks as to the need for defrag on EXT4
> in Linux vs the need for it with NTFS and Windows.
>

I had written a fairly lengthy post on this only to have it eaten before I
hit “Send”.  Grr.

A good place to start reading is the Wikipedia article on filesystem
fragmentation (http://en.wikipedia.org/wiki/File_system_fragmentation) which
provides a good overview of the subject.  Like anything on Wikipedia, you
can spend hours upon hours reading there.

Without going to a great deal of effort (we just got back from Toledo and I
am about ready to have a long, long sleep), operating systems such as DOS
and Windows require filesystem defragmentation as a matter of routine
operation.  The problem could be mitigated somewhat if different types of
files were on different filesystems (e.g., if C:\, C:\Windows, C:\Users,
C:\Program Files and C:\Program Files (x86) were all their own partitions),
because then updates to the operating system or user profiles would have no
effect on each other.  This is one reason why a UNIX system with multiple
partitions does not suffer (as much) from the symptoms of file
fragmentation.  Furthermore, if you can put filesystems that are likely to
suffer a great deal of fragmentation on their own drives, you can reduce the
symptoms even further.

I've never even thought to check fragmentation on my drives at home, nor on
the small business servers that I run; filesystem I/O is not a problem on my
systems in that regard.  I do keep things heavily separated and partitioned,
and I try hard to keep temporary data on RAM disks instead of real
filesystems.  If I do need a large amount of temporary storage on a system,
I'll give it its own dedicated filesystem instead of having it share a mount
point with the root filesystem or similar; I've always found it to be good
practice to keep partitions separated from each other by functional task.
Not only does it mean that fragmentation isn't a problem across those
filesystems, but it means that it's easy to work with backing up and
restoring an individual filesystem based on its purpose (and since some
filesystems change less frequently than others, it is somewhat easier to
back up data efficiently).

Anyway, that's really all I've the energy to spew forth tonight.  Of course,
if you're interested, there is _plenty_ out there to search about and read
up on.  I'd recommend starting with learning about relatively simple
filesystems like the FAT family, and then research progressively more
complex filesystems and what functionality they provide.  Then start looking
into various different implementations of those filesystems (usually,
operating system kernels) to see how they combat (or ignore!) the problems
of filesystem fragmentation and other filesystem agnostic issues.

Filesystems can be a very fascinating thing to learn about...
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