Re: [gentoo-dev] News item review: SquashDelta syncing support

[Diamond <diamond@hi-net.ru>]

On Fri, 15 May 2015 08:23:27 -0700
Dirkjan Ochtman <djc@gentoo.org> wrote:

> On Fri, May 15, 2015 at 7:51 AM, Michał Górny <mgorny@gentoo.org>
> wrote:
> > Starting with Portage 2.2.19, a new SquashDelta syncing method has
> > been introduced. It is meant to provide lightweight and efficient
> > solution for stable systems. The whole repository is contained
> > within a single pre-generated SquashFS image file. The daily
> > snapshot of the repository is first fetched from the mirrors, and
> > afterwards updated in-place using deltas (without repacking).
> 
> This sounds nice, but the news item currently leaves me wondering what
> sort of improvements I should expect. It says the new method is
> "lightweight and efficient", but it would be nice to quantify this a
> little bit, or add a link to a page with more details. I think the
> default sync method in the handbook up to now has always been rsync? A
> comparison (both in terms of upside and in terms of downside) would be
> nice. Also, whether we want to make this the new default at some
> point, and if so, when.
> 
> Cheers,
> 
> Dirkjan
> 
> 

I've read the pdf article of Michał Górny and from my expirience with
emerge-delta-webrsync and app-portage/getdelta in the past this good old
new feature looks mostly useful for bad Internet connections (too slow
or too expensive ones) and looks mostly useless for syncing
relative to rsync method from local mirror like I use
http://mirror.yandex.ru/gentoo-distfiles/
 from my local region.
eix-sync gave me the following statistics (before introducing new
portage sync with repos.conf wich has stopped upgrade in the middle atm
because >=app-portage/layman-2.3.0 haven't been stabilised yet):
 * Time statistics:
    19 seconds for syncing
    17 seconds for eix-update
     1 seconds for eix-diff
    51 seconds total
or this one the other day:
* Time statistics:
    37 seconds for syncing
    11 seconds for eix-update
     1 seconds for eix-diff
    67 seconds total
So it takes usually 15-40 seconds for syncing using usual rsync method.
This deltas have their own drawbacks like "delta is under generation,
please wait half an hour or even more" or "your state is not the same
what was while generating delta on the host and lets do additional work
with more deltas". ))

Although, nice try with experimenting and trying to improve sync
mechanism. )