Hi, I just want to shed light on three arguments against a new custom archive format.
Compressing the files using a standard format (like gz or xz) file-by-file has the advantage of better debuggability. Developers can easily (de)compress or otherwise those files using their standard utilities when trying to debug problems. Using a custom format always makes that process more difficult. In addition, increasingly more file systems support features like block_suballocation, tail packing or tail merging[1]. This drastically reduces the space loss due to files being smaller than the block size. And the third argument is the simplicity of implementation. Just checking .svn/pristines/ab/abcd.gz in addition to .svn/pristines/ab/abcd when searching for a pristine file is much easier to implement. I'm not opposed in general to storing pristines in an archive, but the disadvantages should be weighted in when making the decision. A different, somehow related idea is a common pristine store somewhere in the users directory, shared by several working copies. Especially when checking out several working copies of the same project (or similar branches), this could save a lot of network traffic. Best regards Markus Schaber [1]: http://msdn.microsoft.com/en-us/library/windows/desktop/ee681827%28v=vs.85%29.aspx claims tail packing support for NTFS. http://en.wikipedia.org/wiki/Block_suballocation claims support for Btrfs, ReiserFS, Reiser4, FreeBSD UFS2. And AFAIR, XFS has a similar feature. -- ___________________________ We software Automation. 3S-Smart Software Solutions GmbH Markus Schaber | Developer Memminger Str. 151 | 87439 Kempten | Germany | Tel. +49-831-54031-0 | Fax +49-831-54031-50 Email: m.scha...@3s-software.com | Web: http://www.3s-software.com CoDeSys internet forum: http://forum.3s-software.com Download CoDeSys sample projects: http://www.3s-software.com/index.shtml?sample_projects Managing Directors: Dipl.Inf. Dieter Hess, Dipl.Inf. Manfred Werner | Trade register: Kempten HRB 6186 | Tax ID No.: DE 167014915 -----Ursprüngliche Nachricht----- Von: Mark Phippard [mailto:markp...@gmail.com] Gesendet: Donnerstag, 22. März 2012 16:23 An: Ashod Nakashian Cc: Daniel Shahaf; dev@subversion.apache.org Betreff: Re: Compressed Pristines (Design Doc) On Thu, Mar 22, 2012 at 11:18 AM, Ashod Nakashian <ashodnakash...@yahoo.com> wrote: >>Design-wise I'm a bit surprised that the choice ended up being rolling >>a custom file format. > > Personally I know not of any library that can deliver the requirements > that we need (outlined in the doc). Again, if the requirements are in > question, let's simplify them. If there is such a library, suggesting > it will save us a lot of time and effort. Otherwise, using a Tar-like > container will just not cut it. On the other hand, the proposed custom format > is rather simple and its code shouldn't be complex. In fact, I suspect Tar is > more complex (considering it must store more information than we do). I am not sure what Daniel meant, but I had always just assumed we would simply compress the files in the existing pristines. I think your document does a nice job explaining why that is not good enough. In that sense, I would also say that I was surprised by the choice of a custom file format, but that does not mean I would question it. I think your document does a nice job in revealing some of the subtle complexities of this feature. That gives me more hope on progress towards a solution. -- Thanks Mark Phippard http://markphip.blogspot.com/
