What kind of data storage and processing is needed

[vishalkhialani]

Hi,

So after reading a few posts here I  have realised it a big deal to crawl the web and index all the links.

For that I appreciate seomoz.org's efforts .

I was wondering what kind of infrastructure they might need to get this done ?

cheers,

Vishal

[RyanKent]

Thank you so much Kate for the explanation. It is quite helpful to better understand the process.

[katemats]

Hi vishalkhialani!

I thought I would answer your question with some detail that might satisfy your curiosity (although I know more detailed blog posts are in the works).

For Linkscape:

At the heart of our architecture is our own column oriented data store - much like Vertica, although far more specialized for our use case - particularly in terms of the optimizations around compression and speed.

Each month we crawl between 1-2 petabytes of data, strip out the parts we care about (links, page attributes, etc) and then compute a link graph of how all those sites link to one another (typically between 40-90 billion urls) and then calculate our metrics using those results.  Once we have all of that we then precompute lots of views of the data, which is what gets displayed in Open SIte Explorer or retrieved via the Linkscape api.  These resulting views of the data is over 12 terabytes (and this is all raw text compressed data - so it is a LOT of information).  Making this fast and scalable is certainly a challenge.

For the crawling, we operate 10-20 boxes that crawl all the time.
For processing, we spin up between 40-60 instances to create the link graph, metrics and views.
And the API servers the index from S3 (Amazon's cloud storage) with 150-200 instances (but this was only 10 1 year ago, so we are seeing a lot of growth).

All of this is Linux and C++ (with some python thrown in here and there).

For custom crawl:

We use similar crawling algorithms to Linkscape, only we keep the  crawls per site, and also compute issues (like which pages are duplicates of one another).  Then each of those crawls are processed and precomputed to be served quickly and easily within the web app (so calculating the aggregates and deltas you see in the overview sections).

We use S3 for archival of all old crawls.  Cassandra for some of the details you see in detailed views, and a lot of the overviews and aggregates are served with the web app db.

Most of the code here is Ruby, except for the crawling and issue processing which is C++.  All of it runs on Linux.

Hope that helps explain!  Definitely let me know if you have more questions though!
Kate

[RyanKent]

It is no where near that many. I attached an image of when I saw Rand moving the server to the new building. I think this may be the reason why there have been so many issues with the Linkscape crawl recently.

XhlZi.jpg

[vishalkhialani]

@keri and @Ryan

will ask them. my guess is around a thousand server instances.

[KeriMorgret]

Good answer from Ryan, and I caution that even then you may not get a direct answer. It might be similar to asking Google just how many servers they have. SEOmoz is fairly open with information, but that may be a bit beyond the scope of what they are willing to answer.

[RyanKent]

A question of this nature would probably be best as your one private question per month. That way you will be sure to receive a directly reply from a SEOmoz staff member. You could also try the help desk but it may be a stretch.

All I can say is it takes tremendous amounts of resources. Google does it very well, but we all know they have over 30 billion in revenue generated annually.

There are numerous crawl programs available, but the problem is the server hardware to run them.

I am only responding because I think your question may otherwise go unanswered and I wanted to point you in a direction where you can receive some info.