SymptomsI have a lot of domains on my Parallels Plesk Panel system on Windows platform. The more domains on the server the longer restore process is running. If in the same moment any customer makes changes in his domain hosting configuration then newly created instance of websrvmng.exe process that has to perform this change is getting stacked in queue and waiting until that long process release the IIS metabase.
CauseThis is a well-known Plesk-design problem, where its communication with IIS7 engine is affected. The thing is IIS7 API is not used the same way that IIS6, that is why adding any new account makes metabase overloaded.
ResolutionIIS7 communication engine was improved in Parallels Plesk Panel version 9.5.3. Consider upgrading to this version.
As for the previous Parallels Plesk Panel versions try to avoid hosting more than 200 domains on Windows 2008 server. You may, e.g. migrate part of your domains to another server to avoid slowness on virtual hosting creation or restoring.