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To: "Robin H. Johnson" <robbat2@g.o>
From: Donnie Berkholz <dberkholz@g.o>
Subject: Re: meeting followup: repo layout
Date: Fri, 29 Oct 2010 21:28:34 -0500
On 23:53 Tue 26 Oct     , Robin H. Johnson wrote:
> On Tue, Oct 26, 2010 at 07:15:46PM +0000, Robin H. Johnson wrote:
> > Repo layout
> >  * Natural option (seems to be used by most projects) is one package per repo
> >  * Main problems: how to manage initial clones, updates, package moves, category moves
> >    * The "repo" tool written for Android can handle most of this
> >      * Renaming packages a problem (requires admin participation)
> >        * Average 1-2/week over the past few years
> >      * Moving packages between categories can be done by committers
> The other major problem with splitting the repo, is that the overhead
> that will be imposed by it. This got lost during the talks, but I've
> followed up with warthog9, and the size is going to hurt.
> In an attempt to explain that better, I've laid out below, the (inode)
> overhead costs per checkouts in each VCS, in a variant of O-notation.
> d = number of directories, f = number of files, r = number of
> repositories.
> CVS: O(3d)
> SVN: O(8d + 2f)
> Git: O(35r)

Very interesting numbers, Robin!

By making the (simplistic?) assumption that the above O(foo) is really 
=foo, I attempted to calculate the direct comparisons of disk space that 
follow from the info you provided.

In that case, SVN, Hg and Git all use at least 4x the space of CVS for 
per-package, and SVN doesn't even differentiate between one big repo or 
per-package. A repo-per-package model in Git would be nearly equivalent 
in inode overhead to using SVN. Is that really a bad thing?

With 4K blocks, that works out at roughly 500 MB (CVS) to 2 GB (SVN, 
Git) of inode overhead. I have a hard time imagining people so hard up 
for disk space that they can fit the whole git repo but can't find 
another 1.5 GB.

Based on my current git conversion with a pack size of 1.7 GB, I suppose 
that means the total repo in a git world could vary from ~2 GB all the 
way up to ~4 GB.


Donnie Berkholz
Sr. Developer, Gentoo Linux
pgplYtkC17uTb.pgp (PGP signature)
repo layout & graft / split-history
-- Robin H. Johnson
Notes from a recent meeting; Updated conversion
-- Donnie Berkholz
Re: Notes from a recent meeting; Updated conversion
-- Robin H. Johnson
meeting followup: repo layout
-- Robin H. Johnson
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Updated May 23, 2012

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