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