Dnia 2014-01-18, o godz. 10:08:13 hero...@gentoo.org napisał(a): > Michał Górny <mgo...@gentoo.org> writes: > > > However, it may be actually beneficial to provide other durations, like > > weekly deltas. In my tests, the daily updates for this week summed up > > to almost 50M while the weekly was barely 20M. > > Is there a way to merge the deltas without the original squashfs?
You mean get two deltas and merge them to a single one? I have no idea, honestly :). It may be possible but xdelta3 is hard to use. > how fast is the delta generation? With max compression on 2 GHz amd64, about 15s for a daily delta. A weekly takes 25s. > Or we provide a set of 16,8,4,2,1 day deltas, then > > 16d: 1 piece needed > 8d: 2 needed > 4d: 4 needed > 2d: 8 needed > 1d: 16 needed > > The total of 31 pieces will cover a month (31 days) with at most 5 > deltas to be downloaded. > > e.g. If the system is 19 days old, then we download a 1d, 2d, and 16d. Unnecessarily complex and not worth the effort. Please remember that we're generating deltas against compressed image with metadata cache included. Those are far from optimal, and with your solution you'll quickly run over the original squashfs size. I'm currently working on another solution that should be a bit harder for the server yet much better for users. It assumes we're keeping deltas from N days back to today, i.e.: n-1..n, n-2..n, n-3..n. Any of those deltas is much smaller than two dailies (I'll provide exact numbers when my playground finishes, that is in few hours). You just download the one matching your current image and apply it, and TADAAM, you've got today's snapshot :). -- Best regards, Michał Górny
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