Re: Google Code: Support for Mercurial and Analysis of Git and Mercurial
- From
Johannes Schindelin <johannes.schindelin@gmx.de>
- Date
- Apr 26, 2009, 17:45 UTC
- Message-ID
- <alpine.DEB.1.00.0904261943070.10279@pacific.mpi-cbg.de>
- In-Reply-To
- <49F49AF0.1020301@gmail.com>
Hi,
On Sun, 26 Apr 2009, A Large Angry SCM wrote:
Show 24 quoted lines
> Johannes Schindelin wrote: > > > On Sun, 26 Apr 2009, A Large Angry SCM wrote: > > > > > Another important criteria was which, both or neither of Git and Hg > > > would actually work and perform well on top of Google Code's > > > underling storage system and except to mention they would be using > > > Bigtable, the report did not discuss this. Git on top of Bigtable > > > will not perform well. > > > > Actually, did we not arrive at the conclusion that it could perform > > well at least with the filesystem layer on top of big table, but even > > better if the big tables stored certain chunks (not really all that > > different from the chunks needed for mirror-sync!)? > > > > Back when I discussed this with a Googler, it was all too obvious that > > they are not interested (and in the meantime I understand why, see my > > other mail). > > I don't remember the mirror-sync discussion. But I do remember that when > the discussion turned to implementing a filesystem on top of Bigtable > that would not cause performance problems for Git, my response was that > you'd still be much better off going to GFS directly instead of faking a > filesystem on top of Bigtable without all of the Bigtable limitations.
Umm, GFS is built on top of Bigtable, no?
> Bigtable _is_ appealing to implement the Git object store on. It's too > bad the latency in Bigtable would make it horribly slow.
If you store one object per Bigtable, yes. If you store a few undelta'd objects there, and then use the pack run to optimize those tables, I think it would not be horribly slow. Of course, you'd need to do exactly the same optimizations necessary for mirror-sync, but I might have mentioned that already ;-)
Ciao, Dscho