If you deploy Plesk in a VPS environment, for example, Virtuozzo containers, consider switching Plesk to the VPS-optimized mode. This mode switches off modules that are not critical for hosting services. See the section Apache Modules Switched Off in VPS-Optimized Mode for details.This makes Plesk use less memory than other control panels and provides better utilization of hardware resources and increased density of virtual environments per server.
Note: You can switch only clean Plesk installations to the optimized mode, it is not possible to do this with Plesk installations upgraded from earlier versions. Moreover, you can enable the optimized mode only on fresh installations of Plesk which have not yet been initialized.