Scalability of Orthanc

One of the most common question about Orthanc is: “How many DICOM instances can be stored by Orthanc?”

The source code of Orthanc imposes no such hard limit by itself. At the time of writing, we know that Orthanc is being used in production in hospitals with more than 15TB of data, 125,000 studies and around 50 millions of instances (please get in touch with us if you can share other testimonials).

The stress is actually put on the underlying database engine, and on the storage area (check out How does Orthanc store its database?). As explained in the troubleshooting section, the built-in SQLite database engine should be replaced by an enterprise-ready database engine once Orthanc must store several hundreds of thousands of DICOM instances (check out the PostgreSQL plugins and MySQL/MariaDB plugins). It is also true that the performance of Orthanc in the presence of large databases has continuously improved over time, especially when it comes to the speed of DICOM C-FIND.

Here is a generic setup that should provide best performance in the presence of large databases:

  • Make sure to use the latest release of Orthanc (1.5.4 at the time of writing).
  • We suggest to use the latest release of the PostgreSQL plugin to store the database index (3.1 at the time of writing). Make sure that EnableIndex is set to true.
  • Make sure that run-time debug assertions are turned off. A warning will show in the logs if this is not the case. Note that all pre-built binaries provided by Osimis are correctly configured in that respect.
  • We suggest to use the default filesystem storage area. Of course, make sure that the filesystem is properly backed up, and that technologies such as RAID are enabled. Make sure that the option EnableStorage of the PostgreSQL plugins is set to false.
  • Obviously, the PostgreSQL database should be stored on a high-speed drive (SSD). This is less important for the storage area.
  • The Orthanc configuration file should have the following values for performance-related options (but make sure to understand their implications):
    • StorageCompression = false
    • LimitFindResults = 100
    • LimitFindInstances = 100
    • KeepAlive = true
    • TcpNoDelay = true
    • SaveJobs = false
    • StorageAccessOnFind = Never
  • Make sure to carefully read the logs in --verbose mode, especially at the startup of Orthanc. The logs may contain very important information regarding performance.
  • Make sure to read guides about the tuning of PostgreSQL.