On Fri, Jan 17, 2014 at 8:27 AM, Michał Górny <[email protected]> wrote:
> Hello, all. > > I'm using squashfs to hold my Gentoo repositories on all of my systems > for some time. As you probably know, this allows me to save space while > keeping portage fast. However, it makes updating the tree quite > burdensome and time-consuming. > > We're already hosting daily gx86 tarballs on our mirrors, and deltas > made using diffball. Those can be used with Zac's emerge-delta-webrsync > to get daily updates done with minimal network overhead. Sadly, it > takes the whole process even more time consuming :). > > Therefore, I'd like to suggest an alternative solution that could help > out Gentoo users that use squashfs for gx86 and would like to be able > to get daily updates fast and easy. > > The idea is to host -- along with the tarballs -- daily squashfs images > of gx86 in a chosen format. Additionally, the images would come with > deltas made using xdelta3 or a similar tool. Those deltas -- with > a slight download overhead -- would allow very fast updates > of the squashfs. > > Now some numbers. I did some tests 'converting' late gx86 daily > tarballs to squashfs. I've used squashfs 4.2 with LZO compression > since it's quite good and very fast. > > 96M portage-20140108.sqfs > 96M portage-20140109.sqfs > 96M portage-20140110.sqfs > 96M portage-20140111.sqfs > 96M portage-20140112.sqfs > 96M portage-20140113.sqfs > 97M portage-20140114.sqfs > 97M portage-20140115.sqfs > > For deltas, I've used xdelta3 with max compression (-9) and djw > secondary compression (it gave ~0.1M smaller files than fgk > and ~0.5M gain than with no secondary compression). > > 4,9M portage-20140108.sqfs-portage-20140109.sqfs.vcdiff.djw > 6,3M portage-20140109.sqfs-portage-20140110.sqfs.vcdiff.djw > 5,6M portage-20140110.sqfs-portage-20140111.sqfs.vcdiff.djw > 8,9M portage-20140111.sqfs-portage-20140112.sqfs.vcdiff.djw > 6,3M portage-20140112.sqfs-portage-20140113.sqfs.vcdiff.djw > 7,8M portage-20140113.sqfs-portage-20140114.sqfs.vcdiff.djw > 8,5M portage-20140114.sqfs-portage-20140115.sqfs.vcdiff.djw > > As you can see, the deltas are quite large compared to the actual > changes. However, we could have expected that since we're diffing > a compressed filesystem. What's important, however, is that applying > it takes ~2.5 second on my 2 GHz Athlon64. > It wasn't clear to me, are these trees with metadata included? -A > > So, even with the extra download time, the update is much faster > than recreating the squashfs. And unlike some types of unionfs, > it doesn't come with extra runtime slowdown. > > What do you think? > > -- > Best regards, > Michał Górny >
