Hi,
we are a developers at EMBL-EBI (Cambridge, UK) and we are using
Virtuoso for a project dealing with converting text-mining output as RDF.
We have performance issues at querying time with our Virtuoso instance.
Here is the main info about our environment:
- we are using Virtuoso version 7.2.2. We are allocating 16GB for the
Virtuoso process that is running on a Linux VM having 32 GB of memory.
- our dataset contains 2 billions of triples (50 GB)
- we are not segmenting the db in different files.
- we are experiencing performance issues when the size of the response
of the SPARQL query goes above some threshold.
We query the system using the web service end point (REST api) and
not directly the SPARQL endpoint.
We always make the same SPARQL query using a different identifier,
the retrieved data (triples) varies depending on the identifier.
In some cases it could be more than 5 MB and it responds in more
than 20 seconds. When the number of triples in the response is
particularly high the system is not able to answer generating a
"Transaction timeout" error (20 thousands triple that could generate a
response of more than 20 MB).
Previously we were allocating 24 GB to Virtuoso but after some load
testing we realized that the configuration is more performant with 16 GB.
We tried to reduce the swapping parameter of the Linux Operating system
from 30 to 10 as suggested in the Virtuoso Tuning guide but it did not
improve the performance.
We also tried to follow the instructions reported at
http://docs.openlinksw.com/virtuoso/databaseadmsrv.html#VIRTINI in the
Performance Diagnostics section but we could not spot any particular
problem.
We would appreciate a lot if somebody could advice us on improving the
performances at querying time.
Thanks,
Francesco Talo'
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