So you have 3 3-meg files on a disk, each are contiguous. You erase the
middle one and write a 4 meg file to the disk. Thoeretically, the kernel
will write the first three megs where the deleted one is, and the last meg
to the first meg of the free space. This is called file fragmentation. I
have a large disk that I keep mp3s on, and it has over 80% non-contiguous.
It's not really a problem, except for speed issues. Defragmenting a
partition will noticeably increase read and write speeds to that disk, but
only if you fragmentation is very large. (Don't ask me to define "very
large", that is still being debated among filesystem experts) Since all I
need to do is play the mp3s and serve them out over a smb share to the
network, it's not really a problem and I don't really need to defragment
the filesystem. But if this partition is your /usr or /home, then you may
want to consider defragmenting that partition. You see, every time you
read a fragmented file, the kernel looks up in the superblock where the
first part of the file is, reads it, and then jumps to the next fragment.
(Actually it's a little more complex than that, but let's keep it simple
for now.) The seek time for your disk plays in here for every fragment
the file has, and if you have a large seek time >10ms, then you might get
some speed increase out of defraging. There is a utility called e2defrag,
but I never worked well for me with large partitions (4 gig or bigger),
but you might want to try it.
-CJO-
On Sun, 20 Jun 1999, Sangohn Christian wrote:
>Hello!
>
>Every time my Debian-Linux makes an automatic file system check on all
>partitions after a certain amount of boot ups, the part of "non-contiguous"
>files higher than the last time.
>Is that a problem (I couldn't find the word contiguous in my English-German
>dictionary)?
>If yes how do I fix that?
>
>Thanks.
>
>--
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>
C.J. Oster (Linux Guru/Surge Addict)
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