On 1/03/2016 3:13 p.m., Barry wrote:
Probably a very basic question but it has me puzzled????

I have copied a directory with a dozen or so subdirectories and 4000+
files from an Ext3 filesystem to a Dos (fat32) filesystem on another drive.

I then checked the properties of each  and found that the number of
files and of sub-directories on each is identical, but the sizes in MiB
differs greatly, the dos one being over 5 times the size of the Ext3 one.

Is this because of the differing filesystems , or do I have to now
compare the individual files?


Hm, over 5 times the size... that's a lot... But in principle both ext3 and DOS / FAT allocate disk space only in multiples of their respective block size, so that any file not fitting smoothly into a whole number of blocks will occupy a certain number of full blocks, plus one less than full block. If you have many small files (in the order of up to only a few blocks each) you lose a greater percentage of space due to this.

Now the block sizes for ext3 and FAT are not fixed - they are configurable within a certain range on creation of the file system, from memory somewhere between 1 and 4 KiB.

If your FAT (DOS) FS has larger blocks than the ext3 then it will be less efficient on average for small files. You won't notice this unless you have a large number of small files, though...

Does that sufficiently explain the observed effect, or is there more to it?

Kind regards,

Helmut.

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