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

[Alecks Gates <alecks.g@gmail.com>]

On Tue, Aug 14, 2012 at 3:17 PM, Michael Mol <mikemol@gmail.com> wrote:
> 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

Check out some of the benchmarks on Phoronix[0].  It's definitely not
a win-win scenario, but it seems to be great at random writes and
compiling.  And a lot of those wins are without compress=lzo enabled,
so it only gets better.  I'm not going to say it's the absolute best
out there (because it isn't, of course), but it's at least worth
checking into.  I'm using a standard 2.5" HDD like in this[1] so
perhaps that's why I see the results.

[0] http://www.phoronix.com/scan.php?page=search&q=Btrfs
[1] http://www.phoronix.com/scan.php?page=article&item=btrfs_old_linux31