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From Peter Pöml <Pe...@poeml.de>
Subject Ditching our mirror system for an inferior solution? (was: Re: About Testing the SourceForce Mirror of AOO 3.4)
Date Thu, 12 Apr 2012 23:40:00 GMT
Hi,

Am 03.04.2012 um 18:17 schrieb Roberto Galoppini:
> We at SourceForge have worked the last ten days to line-up dedicated
> infrastructure (including CDN services) to support the upcoming AOO
> download serving test.

I can hardly believe reading this! What's going on? We have an existing (and well working)
mirror network, that handles any required load just fine. It's proven and time-tested. It
has survived all releases with ease. By all calculation, and by practical experience, the
combined upload capacity of the mirrors is sufficient to satisfy the peak download demand
as well as the sustained demand. By the way, the "peak download demand" doesn't really differ
a lot from the day-to-day download demand, contrary to public belief. The mirrors are numerous
and spread around the world, and the chance of a client being sent to a close and fast mirror
is good - better than with a handful of mirrors as is the case with the Sourceforge mirror
network. Sourceforge specializes in something different - providing a myriad of small files
by a set of specialized mirrors. "Normal", plain simple mirrors can't take part in this network
as far as I can tell. Even though the network was considerably extended a few years ago, from
10 (under 10?) to >20 mirrors, this is still a small number of mirrors. (Even though these
are power-mirrors, but those are part of our existing mirror network just as well.)

With our mirror network, mirrors can mirror partial content, so they can provide what's important
in their region, like certain language packs only. This greatly increases the likelyhood of
finding mirrors in remote areas, that don't have hundreds of gigabytes to spare. It's also
unnecessary that mirrors carry old releases that are infrequently downloaded. Mirrors can
run whatever HTTP software they prefer, not only Apache httpd, or even FTP servers. Mirrors
can decide to offer mirroring only in their network/autonomous system/country to limit the
share of requests they get, and from where they get it. Many mirrors don't have good international
connectivity, but can be used well with us nevertheless. We provide cryptohashes, Metalinks,
even P2P links, all fully automatically. That's very important for these unusually large files.
Downloading without error correction is not fun. We select mirrors by GeoIP, but also by geographical
distance as well as network topology, whatever gives a close match, and we already support
IPv6.

It has taken some years to build all this, and a lot of the features were triggered directly
by the work on the OpenOffice.org redirector. Built for OpenOffice.org

The software is the one kind of work that went into it, finding and collecting mirrors the
other thing, building trust and lasting relationship. A mirror network isn't built overnight.

I think there is a danger that the Apache mirror network is equated with the OOo mirror network.
This is a mistake in my view. The large files that we have are a totally different challenge.
It's a huge difference to download 6MB tarballs and 200MB files, both from the users perspective
("why does my file not work, that I waited so long for!?") and from the mirrors perspective
("what are these 200 connections from Chinese IPs on my mirror server!?").
It is important to be able to give mirrors different weight, because they differ vastly in
their capabilities, which can range from 4GBit bandwidth down brittle to 50Mbit somewhere
else. Even inside an "Internet country" like Germany you'll have differences of 100 MBit to
multiple Gbit, and you want to utilize the bandwidth well. We have this working well!

OpenOffice.org used a software called "Bouncer" before switching to MirrorBrain, which was
one of the simpler solutions. I think everybody (who has been in the project a few years)
will agree that we don't want to go back.

So I see that Sourceforge wants to beef up their network by renting a Content Delivery Network
(CDN). Is that needed? yes, because they don't have enough bandwidth in mirrors. Is that a
good idea? I don't think so, but I'm biased, because 1) I don't like advertisements and 2)
I'm strongly rooted in the mirror community with both legs. 

In the mirror community, there is a kind of self esteem among the more ambitious mirror admins:
they believe that stepping in of commercial CDNs is not needed to handle even peak download
demand of the most popular Open Source software. And they work hard for it. Together, we have
proven that the help of commercial CDNs is *not* needed, both with OpenOffice.org and with
OpenSUSE.org. Mirrors have served > 20 GByte per second together. The bandwidth is there!
(In the past, Akamai was used during release peaks with OpenSUSE.org, so I have been there,
and also got interesting insight and numbers there.)

I tried the currently configured download from http://www.openoffice.org/download today (from
a real crappy end user box ;). It was slow and didn't start downloading immediately, but showed
a page full of advertisement that didn't have any relation to OpenOffice.org, wanted to open
a popup (MS IE said that and blocked it) and when the download started, it came from the Swiss
mirror, but I'm in Germany! What's that? Thrown 3 years back in time? Sub-optimal. (I can
guess who pays for the CDN that is rented to help out: advertising.)


Do you really want to ditch what we have built? Ditching the system that improved downloading
OpenOffice.org in the farthest corners of the world? Exchanging it against a handful of Sourceforge
mirrors, and 250 Apache mirrors, many of which lack the capability? Some are big, but many
will be far from having the bandwidth to deliver large files. 

Something that Apache's mirror system also can't do is sending me to my local mirror (my very
ISP in my city runs a mirror, and my home IP is in their netblock). Apache mirror system sends
me to *any* mirror in my country, while our current solution recognizes the network topology
and lets me download from the local mirror. Especially with large files, that's very nice
both for the ISP and for me as user. Sourceforge can theoretically do this (because they use
a part of MirrorBrain for that purpose!) but don't have enough mirrors to play this out. This
is not only useful with single ISPs, if they have a mirror; it's also useful with autonomous
systems (AS) of networks that share a backbone, like most German universities in AS680 here
in Germany. 


So we will have a *technically inferiour* solution in the future? That's not the Apache way,
is it?

I have been told more than once, on this list, that "it will be the Apache mirror system and
nothing else". I didn't understand the reasons (except for policy, no special treatment for
individual projects), but it won't work that way IMO.

Now it seems to me that the Apache mirror system seeked the help of Sourceforge.net. If that
means that some doubts crept up, then I share those doubts. But I don't see Sourceforge.net
as the solution either, as explained above. They have their merits, and I like their dedication
and the specialized system they've built (with features that I'm envious of!), but I think
our existing solution is better suited. And not only that, IMO it is a very important prerequisite
of being successful. No well-working downloads, no luck with distributing FOSS that consists
of large files. 

Thanks for reading that far,
Peter


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