AW: Compressed Pristines (Design Doc)
From: Markus Schaber <m.schaber_at_3s-software.com>
Date: Thu, 22 Mar 2012 15:48:53 +0000
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. 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.
-- ___________________________ 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: firstname.lastname@example.org | 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:markphip_at_gmail.com] Gesendet: Donnerstag, 22. März 2012 16:23 An: Ashod Nakashian Cc: Daniel Shahaf; dev_at_subversion.apache.org Betreff: Re: Compressed Pristines (Design Doc) On Thu, Mar 22, 2012 at 11:18 AM, Ashod Nakashian <ashodnakashian_at_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/Received on 2012-03-22 16:49:31 CET
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