Any tips for improving the performance of cloning large repositories?

Hi,

We've migrated our old CVS repository into GIT without too many issues. However now we are rolling out the usage of the new repository we are hitting some performance bottlenecks, especially on the initial clone (something our buildbot instance does a lot).

Our repo is large, my .git is around 2.5G although the central repo has a 1.7Gb single pack file. However some machines handle the cloning better than others. For one thing the clone process seems to involve the receiving side needing a large glob of memory which causes problems when there is memory pressure.

I've tried tweaking the pack size from unlimited to 256m but this seems to have increased the clone time as the receiving end attempts to re-pack everything back into an uber-pack.

Another thing that I've noticed is very high systime on the receiving machines as ethernet and disk I/O is heavily hit.

So what I'm looking for are some tips on how I can tweak configurations to make the clone process a little less I/O and memory heavy. Any suggestions?

One thing I did try was a rsync'ed local repo in /var/cache/repos which the clone command used for reference with something like:

git clone --local --reference /var/cache/repo.git git://repo/repo.git

But that didn't help as it seems to copy the whole thing anyway.