Re: Why btrfs inline small file by default?

[Hugo Mills <hugo@carfax.org.uk>]

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On Tue, Oct 30, 2012 at 10:14:12PM +0000, Hugo Mills wrote:
> On Wed, Oct 31, 2012 at 05:40:25AM +0800, ching wrote:
> > On 10/30/2012 08:17 PM, cwillu wrote:
> > >>> If there is a lot of small files, then the size of metadata will be
> > >>> undesirable due to deduplication
> > >>
> > >> Yes, that is a fact, but if that really matters depends on the use-case
> > >> (e.g., the small files to large files ratio, ...). But as btrfs is designed
> > >> explicitly as a general purpose file system, you usually want the good
> > >> performance instead of the better disk-usage (especially as disk space isn't
> > >> expensive anymore).
> > > As I understand it, in basically all cases the total storage used by
> > > inlining will be _smaller_, as the allocation doesn't need to be
> > > aligned to the sector size.
> > >
> > 
> > if i have 10G small files in total, then it will consume 20G by default.
> 
>    If those small files are each 128 bytes in size, then you have
> approximately 80 million of them, and they'd take up 80 million pages,
> or 320 GiB of total disk space.

   Sorry, to make that clear -- I meant if they were stored in Data.
If they're inlined in metadata, then they'll take approximately 20 GiB
as you claim, which is a lot less than the 320 GiB they'd be if
they're not.

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
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             --- I always felt that as a C programmer, I ---             
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