Varnish Enterprise 6.0.13r2 Release

Published June 10, 2024.

Important update

Please note that there is a known issue with MSE 4 in this release. This is described on our Known Issues page.

About the release

This release introduces Massive Storage Engine 4 (MSE4), a few minor features and some bug fixes. Please see the Changelog for more information.

For easy transition between MSE3 and MSE4, Varnish Enterprise will contain both versions going forward. Environments using MSE3 will continue to use MSE3 after upgrading to 6.0.13r2, given that the configuration remains unchanged. The varnishd command line parameter -s is used to select which version to use.

Important: All users of Varnish Enterprise upgrading from version 6.0.12r9 or lower are encouraged to test their VCL with this release before upgrading. If you encounter VCL compilation failures due to invalid VMOD usage, you will need to update your VCL before upgrading. If this VCL has never caused a problem for you before, it is likely that this VCL code was never reached.

Important: All users of Varnish Enterprise in-process TLS upgrading from version 6.0.13r1 or lower are encouraged to test their HTTPS setup before upgrading. New stricter coherence checks could prevent a restart of the service. If a certificate was loaded with incompatible ciphers, these ciphers could not be presented during a handshake. They must be removed from the configuration from 6.0.13r2 on.


MSE4 was created to further improve the performance and resilience of caches with a large number of objects:

  • The memory and book footprint for each object has been optimized, which makes it possible to fit more objects in each cache.
  • Writes to the book are now journaled, which reduces the number of IOPS and reduces the reliance on fast disks.
  • Resource usage limits (or quotas) can be applied to categories of objects, which makes it possible to partition the cache.
  • Checksums ensure that random bit-flips on storage devices are detected and that affected objects are removed.
  • Safe handling of disk failures during runtime makes it possible for individual disks to fail without disrupting the rest of the service.
  • Failed disks can be replaced and reinitialized without disrupting the service.

MSE4 has been through tests in the lab and is now ready for production workloads. If you want to upgrade to MSE4 and would like to have guidance along the way, please reach out to