Re: [gentoo-user] Fast file system for cache directory with lot's of files

[Michael Mol <mikemol@gmail.com>]

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On Tue, Aug 14, 2012 at 3:55 PM, Alecks Gates <alecks.g@gmail.com> wrote:

> On Tue, Aug 14, 2012 at 12:50 PM, Michael Hampicke <gentoo-user@hadt.biz>
> wrote:
> > Am 14.08.2012 19:42, schrieb Volker Armin Hemmann:
> >> Am Dienstag, 14. August 2012, 13:21:35 schrieb Jason Weisberger:
> >>> Sure, but wouldn't compression make write operations slower?  And
> isn't he
> >>> looking for performance?
> >>
> >> not really. As long as the CPU can compress faster than the disk can
> write
> >> stuff.
> >>
> >> More interessting: is btrfs trying to be smart - only compressing
> compressible
> >> stuff?
> >>
> >
> > It does do that, but letting btrfs check if the files are already
> > compressed, if you know, that they are compressed, is a waste of cpu
> > cycles :)
> >
>
> Also look into the difference between compress and compress-force[0].
> I wonder how much overhead checking whether or not to compress a file
> costs.  I use mount options similar to Helmut and get great results:
> defaults,autodefrag,space_cache,compress=lzo,subvol=@,relatime
>
> But most of my data is compressible.  Compression makes such a huge
> difference, it surprises me.  Apparently on this Ubuntu system it
> automatically makes use of all files on / as a subvolume in "@".
> Interesting.
>

Huge difference, how?

Could we see some bonnie++ comparisons between the various configurations
we've discussed for ext4 and btrfs? Depending on the results, it might be
getting time for me to take the plunge myself.

-- 
:wq

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