Disk defragmenter in Linux

[Tim]

Tony Nelson:
>> The opinion that EXT2 doesn't need defragmenting is based on only a
>> filesystem-level view of the problem, and doesn't consider data read and
>> write performance.  EXT2 does make an effort to keep data only a short seek
>> away ("clustered").  With this clustering, the filesystem operations of
>> adding, removing, extending, and shortening files are not much affected by
>> fragmentation.
>> 
>> With EXT3 (journalling), which always writes data to a new place, updates
>> the filesystem info, and then frees the old data (roughly speaking),
>> fragmentation is a way of life, and there isn't much to be done about it.
>> Clustering helps by keeping the seeks relatively short, if there is space
>> nearby.

Mike McCarty:
> I've heard this argument before, quite a few times in fact. It ignores
> one big fact of life with regards to discs. Almost all the data on
> my disc are *static*. They don't change. And so having files (like
> /bin/ls, for example) be contiguous saves enormously when they are
> read.

But such (static) data doesn't get fragmented, it stays as it was
original written.  It's changing files that become fragmented, and newly
written ones that have to fit into the holes of a fragmented drive.  And
since the general advice is to keep /home on a separate partition, for
many good reasons, user files should't affect system and application
files.

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