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Full Discussion: Why we don't need to defrag UNIX FS?
Special Forums Hardware Filesystems, Disks and Memory Why we don't need to defrag UNIX FS? Post 302451143 by Corona688 on Sunday 5th of September 2010 11:21:32 PM
Old 09-06-2010
Quote:
Originally Posted by amro1
We DO need from time to time to defrag UNIX related filesystem. The problem is that unlike NTFS (which is VERY GOOD, well designed, originated in absolutely terrific OpenVMS, file system)
MS must have made an absolute hash of it, then because, as I've said, I've seen it fragment terribly on drives only 50% full. It certainly doesn't seem to make any effort to obey your ideal of squashing everything at the head of the drive, either.
Quote:
However, if you on single drive PC with Linux on it and do something that makes a lot of small files, then removes them and then do it over again, your system will be fragmented as a hell.
I use a distro that keeps 1.9 gigs of metadata in a tree of 100,000 tiny files with frequent replacement. I've seen ReiserFS fragment badly on that(the files didn't fragment, but the directories themselves did, leading to very slow ls), but not the more common Linux filesystems.
Quote:
By doing that, the restored files fill into the drive one by another, no gaps and no interleaving.
You've got an odd idea of fragmentation. It doesn't mean "all files in one giant clump at the start of the drive", which is a recipe for fragmentation -- growing files will have no room to expand, and get scattered in pieces when they do.

And there's certainly better alternatives to dumping the entire filesystem, like shake.
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LEARN ABOUT DEBIAN

e4defrag

E4DEFRAG(8)						      System Manager's Manual						       E4DEFRAG(8)

NAME

       e4defrag - online defragmenter for ext4 filesystem

SYNOPSIS

       e4defrag [ -c ] [ -v ] target ...

DESCRIPTION

       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.

       target is a regular file, a directory, or a device that is mounted as ext4 filesystem.  If target is a directory, e4defrag reduces fragmen-
       tation  of all files in it. If target is a device, e4defrag gets the mount point of it and reduces fragmentation of all files in this mount
       point.

OPTIONS

       -c     Get a current fragmentation count and an ideal fragmentation count, and calculate fragmentation score based on them. By seeing  this
	      score, we can determine whether we should execute e4defrag to target.  When used with -v option, the current fragmentation count and
	      the ideal fragmentation count are printed for each file.

	      Also this option outputs the average data size in one extent. If you see it, you'll find the file has ideal  extents  or	not.  Note
	      that the maximum extent size is 131072KB in ext4 filesystem (if block size is 4KB).

	      If this option is specified, target is never defragmented.

       -v     Print error messages and the fragmentation count before and after defrag for each file.

NOTES

       e4defrag  does  not  support swap file, files in lost+found directory, and files allocated in indirect blocks. When target is a device or a
       mount point, e4defrag doesn't defragment files in mount point of other device.

       Non-privileged users can execute e4defrag to their own file, but the score is not printed if -c	option	is  specified.	Therefore,  it	is
       desirable to be executed by root user.

AUTHOR

       Written by Akira Fujita <a-fujita@rs.jp.nec.com> and Takashi Sato <t-sato@yk.jp.nec.com>.

SEE ALSO

       mke2fs(8), mount(8).

e4defrag version 2.0						     May 2009							       E4DEFRAG(8)
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