It maybe that SSD is the important factor.
1/ From a while ago, on truthy:
https://lists.apache.org/thread.html/70dde8e3d99ce3d69de613b5013c3f4c583d96161dec494ece49a412%40%3Cusers.jena.apache.org%3E
before tdb2.tdbloader was a thing.
2/ I did some (not open) testing on a mere 800M and tdb2.tdbloader with
a Dell XPS laptop (2015 model, 16G RAM, 1T M.2 SSD) and a big AWS server
(local NVMe, but virtualized, SSD).
The laptop was nearly as fast as a big AWS server.
My assumption was that as the database grew, RAM caching become less
significant and the speed of I/O was dominant.
FYI When "tdb2.tdbloader --loader=parallel" gets going it will saturate
the I/O.
----
I don't have access to hardware (or ad hoc AWS machines) at the moment
otherwise I'd give this a try.
Previously, downloading the data to AWS is much faster and much more
reliable than to my local setup. That said, I think dumps.wikimedia.org
does some rate limiting of downloads as well or my route to the site
ends up on a virtual T3 - I get the magic number of 5MBytes/s sustained
download speed a lot out of working hours.
Andy
On 09/06/2020 08:04, Wolfgang Fahl wrote:
Hi Johannes,
thank you for bringing the issue to this mailinglist again.
At
https://stackoverflow.com/questions/61813248/jena-tdbloader-performance-and-limits
there is a question describing the issue and at
http://wiki.bitplan.com/index.php/Get_your_own_copy_of_WikiData#Test_with_Apache_Jena
a documentation of my own attempts. There has been some feedback by a
few people in the mean time but i have no report of a success yet. Also
the only hints to achieve better performance are currently related to
RAM and disk so using lots of RAM (up to 2 Terrrabyte) and SSDs (also
some 2 Terrabyte) was mentioned. I asked at my local IT center and the
machine with such RAM is around 30-60 thousand EUR and definitely out of
my budget. I might invest in a 200 EUR 2 Terrabyte SSD if i could be
sure that this would solve the problem. At this time i doubt it since
the software keeps crashing on me and there seem to be bugs in Operating
System, Java Virtual Machine and Jena itself that prevent the success as
well as the severe degradation in performance for multi-billion triple
imports that make it almost impossible to test given a estimated time of
finish of half a year on (old but sophisticated) hardware that i am
using daily.
Cheers
Wolfgang
Am 08.06.20 um 17:54 schrieb Hoffart, Johannes:
Hi,
I want to load the full Wikidata dump, available at
https://dumps.wikimedia.org/wikidatawiki/entities/latest-all.ttl.bz2 to use in
Jena.
I tried it using the tdb2.tdbloader with $JVM_ARGS set to -Xmx120G. Initially,
the progress (measured by dataset size) is quick. It slows down very much after
a couple of 100GB written, and finally, at around 500GB, the progress is almost
halted.
Did anyone ingest Wikidata into Jena before? What are the system requirements?
Is there a specific tdb2.tdbloader configuration that would speed things up?
For example building an index after data ingest?
Thanks
Johannes
Johannes Hoffart, Executive Director, Technology Division
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