Re: Quota definitions

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, Jul 28, 2009 at 06:36:56PM +0000, David Holland wrote:
> On Tue, Jul 28, 2009 at 01:23:39PM +0200, Manuel Bouyer wrote:
>  > I would go with a new format. The current format is a table indexed
>  > by uid or gid. If you use large uid you get a very large sparse file.
>  > A different indexing scheme is needed.
> 
> I'm not convinced. Linux did this and I don't really see the point -
> instead of reusing the FS's tree structure for managing a sparse file,
> they added another layer of tree structure, which buys complexity and
> recovery problems and not a whole lot else.

This huge sparse file cause issues too; some tools don't deal properly
with sparse files. Now, if the file is hidden most of these issues go away.

> 
> Because uids mostly tend to come in contiguous sequences, I'm not
> convinced that in practice one will tend to see quota files with lots
> of blocks that each hold the info for one user and are otherwise
> empty. Except maybe on large installations with lots of uids and lots
> of uid turnover, but even then I expect a much bigger problem is that
> quota records for removed users probably aren't ever G/C'd.

Yes, that's another issue. The uid turnover also leads to a sparse uid
map.


-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--