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.