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This is an output from dumpe2fs:

root: ~/# dumpe2fs -h /dev/sdb3 | grep -i 'fragment|block size'
dumpe2fs 1.39 (29-May-2006)
Block size:               4096
Fragment size:            4096
Fragments per group:      32768

Is this related to disk fragmentation?

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No. ext3fs doesn't support block fragmentation so a one byte file will use a whole 4096 block.

On the opposite, for example UFS supports four fragments in a block so small files won't fill a file system as fast as they will do on ext3fs.

This is unrelated to disk fragmentation which is about file data blocks not being contiguous and sequential.

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Thanks for the answer. The mkfs manual is very cryptic-only a one liner for the "-f fragment-size" option. If block fragmentation is not supported in ext2/3/4, why does the -f option appear in the mke2fs manual? Nothing serious, just curious. – JBraganza Jul 9 '11 at 0:50
Just in case someone want to implement it. See the BUGS section in the very same manual page: mke2fs accepts the -f option but currently ignores it because the second extended file system does not support fragments yet. – jlliagre Jul 9 '11 at 1:27
It is one of those things that was put in as a planned feature, but never implemented. – psusi Jul 9 '11 at 1:28
@psusi: actually, it's one of those things that was put to make ext2fs more like UFS and FFS. Probably noone ever expected it to be implemented in the future. – ninjalj Jul 10 '11 at 20:38
At least the manual page writer expected it to be implemented. – jlliagre Jul 10 '11 at 21:51

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