Defragmentation in Linux ?

[Abraxas]

I'm pretty sure PCLinuxOS (Linux, in general) does not need defragmenting. I feel I've read somewhere this is the case. I no longer use any form of Windows, I do use External Hard Drives however, which I feel could benefit from being defragmented. I may be wrong. 

Back when I was in the Windows world people often bickered that Defragging was a waste of time. In fact they bickered about heaps of things. We all make judgements according to our experiences.
I found Defragging useful, the Hard drive seemed to run better, so I did it.
Before installing a PCLinuxOS Distro as Dual Boot with Windows I would Defrag the Hard Drive maybe three times to ensure no stray Win System files were overwritten.
I run USB flash drives with movies on them on my T.V.
I used to defrag them as sometimes they would seize up, which could be a problem with the Flash Drive, but often it fixed the problem.
1.) Is there a Linux defragmentation program ?
2.) How come Linux runs so well without defragmenting, or have I got this wrong ?
Thanks,

francis

[The Chief]

It's not so much Linux as the file systems in use. 

Linux is typically ext3 or 4 (or related) file systems, which are designed not to get fragmented.  If you install and run Linux on an disk formatted for Fat32 or NTFS (entirely possible), it will have very nearly the same fragmentation problems Windows has. 

On the the other hand, if it was possible to install Windows on an ext3 or 4 file system (AFAIK it isn't), it's fragmentation problems would pretty much go away.

Defragger for Linux?  Maybe, but I don't remember hearing of one.

[T6]

"If you install and run Linux on an disk formatted for Fat32 or NTFS"

afik, this can't be done or install windows on ext4

i remember other posts asking this question, someone mentioned that ext4 does get fragmented but this doesn't impact the performance of the os, or at least it never did on pclinux 2007, the almost 3 years i used it with ext3

or pclinux 2010, almost two years using it now with ext4

the files tend to be written on a more ordered way in the hard disk, it is more a be ordered thing that linux does better

if you take time of the boot process now and in two years, the boot process might be the same or smaller, each new kernel tends to improve everything

a usb flash device does get fragmented, to avid fragmentation all you have to do is copy files to a hard disk, format the drive and copy the files back, it is a simple way to defrag those drives

[Bald Brick]

francis,

There are defraggers for Linux. A couple of years ago there were links to several of them in a post on this very forum. I can't find that post anymore, but Google might be of assistance here. (Note that normally you can't defrag a Linux partition that is currently in use: you have to run the defragger from a live CD or from an install on another partition.)

On the other hand, there's usually no need to defrag a Linux filesystem until a partition gets very full. On a Windows filesystem files are stacked like containers on a cargo ship without any space between them. On a Linux filesystem you start out with quite a lot of space between the files. So when you replace a file in Windows with a just slightly larger version the file is immediately fragmented: the original slot is too small. In Linux the original slot is usually large enough because of the extra space before and after it. So: no fragmentation before the partition really starts to fill up.

If you save movies on a Windows formatted partition they will stack up very neatly. But if you delete some of the movies and replace them with something else you should defrag the partition even if you are running Linux. Or, preferably, do what T6 recommended: "copy files to a hard disk, format the drive and copy the files back".

[MtnMan]

On the other hand, there's usually no need to defrag a Linux filesystem until a partition gets very full. On a Windows filesystem files are stacked like containers on a cargo ship without any space between them. On a Linux filesystem you start out with quite a lot of space between the files. So when you replace a file in Windows with a just slightly larger version the file is immediately fragmented: the original slot is too small. In Linux the original slot is usually large enough because of the extra space before and after it. So: no fragmentation before the partition really starts to fill up.

I like that explanation.  I may be wrong but I think that AHCI Sata drives have Native Command Queuing supported in the Linux kernel which would lessen any effects of fragmentation if it existed.  Since this concept is a carry-over from windows (like anti-virus) I thought this was an interesting read from a windows perspective.

http://winhlp.com/node/82

[Bald Brick]

I did some googling anf found these links.

The first one gives an explanation very similar to what I wrote in my first post. It's five years old so I don't know how relevant it is today. But here it is: http://geekblog.oneandoneis2.org/index.php/2006/08/17/why_doesn_t_linux_need_defragmenting.

The second one is a link to a defragger: http://vleu.net/shake/.

The third one is a link to a defragging script by Con Kolivas: http://ck.kolivas.org/apps/defrag/defrag-0.08/defrag.

Also, do a search for the ext4 defragger e4defrag.

[T6]

ahci, i had to disable everything about it on my netbook so i could install pclinux on it

[AS]

ahci, i had to disable everything about it on my netbook so i could install pclinux on it

when ? I mean few time ago or several years ago ?

[Abraxas]

Hey thanks The Chief, T6, and Bald Brick ! Some very interesting info.
It's no big deal, just something I'd been wondering about for ages.
I run FS ext4, I think it's default filesystem in Linux these days, not an expert.
Did a complete wipe of the Hard Drive and got rid of Windows back in July,and installed PCLinuxOS 2011.06 'MiniMe' .
I found after dual booting into WinXP after using PCLinuxOS for a few days was quite depressing. Slow,... Double clicking, updating AV software, security updates, and on and on, so after making a huge 'BooBoo' one day ( It's a long story  ) Mr. O-P was kind enough to help me set up the Partitions, etc.

If you save movies on a Windows formatted partition they will stack up very neatly. But if you delete some of the movies and replace them with something else you should defrag the partition even if you are running Linux. Or, preferably, do what T6 recommended: "copy files to a hard disk, format the drive and copy the files back".

Interesting with Flash drives, I'd tried that once. Copying all files to a directory, formatting the thing, then copying the files back.
Just today was using Bleachbit, or mainly getting familiar with it, and thought it couldn't hurt to use it to erase the files on a USB Flash drive, as a way of Formatting it. Seems to have worked. I had watched the .Avi files I had on it, and had originals backed up. As I said I pop  flash drives into my T.V., if the files are fragmented it isn't much fun. Very rare these days to have any problems though.
Again thankyou for your feedback, just about no maintenance to do except have fun 
It has however been a steep learning curve over three years to get to were I'm at, which is still a 'newby'.

[T6]

ahci, i had to disable everything about it on my netbook so i could install pclinux on it

when ? I mean few time ago or several years ago ?

september last year

[AS]

ahci, i had to disable everything about it on my netbook so i could install pclinux on it

when ? I mean few time ago or several years ago ?

september last year

you could try to change it temporarily, boot a recent kernel/liveCD, and watch at dmesg for some hints ... it seem strange to me that AHCI could actually be an issue ...

[Vortеx]

Or, preferably, do what T6 recommended: "copy files to a hard disk, format the drive and copy the files back".

Just deleting all files isn't enough?

[T6]

"Just deleting all files isn't enough?"

yes, it should be enough but i have to "fix" partitions and formats made by windows machines so many times that i just do the whole thing, two birds one stone comes to mind

"you could try to change it temporarily, boot a recent kernel/liveCD, and watch at dmesg for some hints ... it seem strange to me that AHCI could actually be an issue"

if i do that, xp could have problems to boot and pclinux is doing fine, that ntbook is dualbooting and that particular change doesn't offer much to me but if i enable it, linux can't see the hard disk immediately

[MtnMan]

if i do that, xp could have problems to boot and pclinux is doing fine

If the correct driver is not installed or slip streamed when xp is installed it will not boot.  I have installed the driver post xp install but it is complicated and as you indicated maybe not worth the effort.   

but if i enable it, linux can't see the hard disk immediately

There is a boot delay for BIOS to set up AHCI but I have never had a problem with any Linux install and that delay has nothing to do with Linux - at least on my computer.

[T6]

sorry, i must rephrase that, linux installer can't see the hard disk

if i disable ahci linux can see the hard disk

at least that was with 2010.1, haven't tested 2011