Re: git repository size / compression

["Carlos Martín Nieto" <cmn@elego.de>]

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On Thu, 2011-09-08 at 21:37 -0500, neubyr wrote:
> I have a test git repository with just two files in it. One of the
> file in it has a set of two lines that is repeated n times.
> e.g.:
> {{{
> $ for i in {1..5}; do cat ./lexico.txt >> lexico1.txt &&  cat
> ./lexico.txt >> lexico1.txt && mv ./lexico1.txt ./lexico.txt;  done
> }}}
> 

So you've just created some data that can be compressed quite
efficiently.

> I ran above command few times and performed commit after each run. Now
> disk usage of this repository directory is mentioned below. The 419M
> is working directory size and 2.7M is git repository/database size.
> 
> {{{
> $ du -h -d 1 .
> 2.7M    ./.git
> 419M    .
> 
> }}}
> 
> Is it because of the compression performed by git before storing data
> (or before sending commit)??
> 

Yes. Git stores its objects (the commit, the snapshot of the files,
etc.) compressed. When these objects are stored in a pack, the size can
be further reduced by storing some objects as deltas which describe the
difference between itself and some other object in the object-db.

> Following were results with subversion:
> 
> Subversion client (redundant(?) copy exists in .svn/text-base/
> directory, hence double size in client):
> {{{
> $ du -h -d 1
> 416M    ./.svn
> 832M    .
> }}}

Subversion stores the "pristines" (which is the status of the files in
the latest revision) inside the .svn directory. I wouldn't call this
copy redundant, though, as it allows you to run diff locally. The
pristines are stored uncompressed, which is why you half of the space is
taken up by the .svn directory.

> 
> Subversion repo/server:
> {{{
> $ du -h -d 1
>  12K    ./conf
> 1.2M    ./db
>  36K    ./hooks
> 8.0K    ./locks
> 1.2M    .
> }}}

I don't know how the repository is stored in Subversion, but it may also
be compressed. You may be able to reduced your git repository size by
(re)generating packs with 'git repack' and doing some cleanups with 'git
gc', but the repository size is not often a concern.

   cmn



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