On Tue, Aug 07, 2012 at 08:22:21PM +0200, Felix Natter wrote: > I read this: > http://metalinguist.wordpress.com/2007/12/06/the-woes-of-git-gc-aggressive-and-how-git-deltas-work/ > where > git repack -a -d --depth=250 --window=250 > is mentioned as a (recommended) alternative to git gc --aggressive. Note how old that post is. In fact, on the very same day it was posted, the discussion on the mailing list resulted in this commit: commit 1c192f3442414a6ce83f9a524806fc26a0861d2d Author: Johannes Schindelin <Johannes.Schindelin@xxxxxx> Date: Thu Dec 6 12:03:38 2007 +0000 gc --aggressive: make it really aggressive The default was not to change the window or depth at all. As suggested by Jon Smirl, Linus Torvalds and others, default to --window=250 --depth=250 So the packing parameters are the same these days for either method. Note that "git gc --aggressive" will also use "-f" to recompute all deltas. This is more expensive, but gives git more flexibility if the old deltas were sub-optimal (typically, this is the case if the existing pack was generated by fast-import, which favors speed of import versus coming up with an optimal storage pattern). > So my questions are: > > 1. is the above repack command (with --depth=500) safe? Of course I want > to be absolutely sure that our repo will be consistent. > Do I need another command ("git gc", "git prune") as well? Yes, it's safe. Changing the depth parameter can never lose data. However, it's probably not a good idea for two reasons: 1. It probably does nothing. You're not likely to hit a 500-depth delta chain (the point of the "250" in --aggressive is that it is already ridiculously high). 2. Even if you did come up with a 500-depth delta chain, it may not be a good tradeoff. You might save a little bit of space, but keep in mind that to generate the object data, it means that git will have to follow a chain of 500 deltas to regenerate the object. Of course, every workload is different. One can develop pathological cases where --depth=500 saves a lot of space. But it's unlikely that it is the case for a normal repository. You can always try both and see the result. In fact, I'd also test how just "git gc" behaves versus "git gc --aggressive" for your repo. The former is much less expensive to run. You really shouldn't need to be running "--aggressive" all the time, so if you are looking at doing a nightly repack or similar, just "git gc" is probably fine. -Peff -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html