[lug] du vs df

[Bear Giles]

Sparse files are/were widely used in hash tables. (That's one of the uses
in the scenario I mentioned above.) I know browsers use something like that
- why you can have massive amounts of disk space released when a browser
closes.

(The SQLite files are sparse but the holes aren't very large. It must be
something else consuming all of the extra space.)


On Mon, Mar 11, 2013 at 5:55 PM, Zan Lynx <zlynx at acm.org> wrote:

> On 03/11/2013 04:46 PM, Michael J. Hammel wrote:
> > And then, when the file went away, that
> > space cleared out, in increments, very fast (but not immediately, as you
> > might suspect with clearing an inode).
> That is the background deletion happening, as I mentioned that EXT4
> does. I guess EXT3 does it too.
>
> There is a lot of work to be done in various places to update the
> tracking information. I think EXT2/3/4 uses block maps, indirect block
> maps, double indirect block maps and possibly triple indirect block
> maps. Each of these need to be marked clear all the way down the
> structure during a delete.
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