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Hello, all. |
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I'm using squashfs to hold my Gentoo repositories on all of my systems |
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for some time. As you probably know, this allows me to save space while |
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keeping portage fast. However, it makes updating the tree quite |
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burdensome and time-consuming. |
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We're already hosting daily gx86 tarballs on our mirrors, and deltas |
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made using diffball. Those can be used with Zac's emerge-delta-webrsync |
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to get daily updates done with minimal network overhead. Sadly, it |
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takes the whole process even more time consuming :). |
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|
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Therefore, I'd like to suggest an alternative solution that could help |
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out Gentoo users that use squashfs for gx86 and would like to be able |
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to get daily updates fast and easy. |
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|
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The idea is to host -- along with the tarballs -- daily squashfs images |
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of gx86 in a chosen format. Additionally, the images would come with |
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deltas made using xdelta3 or a similar tool. Those deltas -- with |
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a slight download overhead -- would allow very fast updates |
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of the squashfs. |
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|
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Now some numbers. I did some tests 'converting' late gx86 daily |
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tarballs to squashfs. I've used squashfs 4.2 with LZO compression |
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since it's quite good and very fast. |
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|
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96M portage-20140108.sqfs |
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96M portage-20140109.sqfs |
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96M portage-20140110.sqfs |
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96M portage-20140111.sqfs |
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96M portage-20140112.sqfs |
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96M portage-20140113.sqfs |
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97M portage-20140114.sqfs |
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97M portage-20140115.sqfs |
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|
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For deltas, I've used xdelta3 with max compression (-9) and djw |
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secondary compression (it gave ~0.1M smaller files than fgk |
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and ~0.5M gain than with no secondary compression). |
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|
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4,9M portage-20140108.sqfs-portage-20140109.sqfs.vcdiff.djw |
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6,3M portage-20140109.sqfs-portage-20140110.sqfs.vcdiff.djw |
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5,6M portage-20140110.sqfs-portage-20140111.sqfs.vcdiff.djw |
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8,9M portage-20140111.sqfs-portage-20140112.sqfs.vcdiff.djw |
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6,3M portage-20140112.sqfs-portage-20140113.sqfs.vcdiff.djw |
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7,8M portage-20140113.sqfs-portage-20140114.sqfs.vcdiff.djw |
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8,5M portage-20140114.sqfs-portage-20140115.sqfs.vcdiff.djw |
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|
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As you can see, the deltas are quite large compared to the actual |
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changes. However, we could have expected that since we're diffing |
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a compressed filesystem. What's important, however, is that applying |
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it takes ~2.5 second on my 2 GHz Athlon64. |
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|
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So, even with the extra download time, the update is much faster |
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than recreating the squashfs. And unlike some types of unionfs, |
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it doesn't come with extra runtime slowdown. |
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|
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What do you think? |
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|
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-- |
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Best regards, |
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Michał Górny |
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