Have you upgraded to 4.8 or 4.9, which I heard is a lot better? Or do they still have similar problems w/ Nepomuk and Strigi?
I'm running KDE 4.8.4, which is what is in Debian Unstable. Before a presentation I did on KDE4 for my local lug I tried Strigi/Nepomuk features again in KDE4.8 and performance was again terrible -- many hours of 100% CPU time during the indexing process. [IIRC on the same P4 system this process took somewhere between 14 to 18 hours to index a home directory with 30 GB of stuff in it, and I think the resulting Virtuoso database was about 1 GB.] The reason is that Nepomuk/Strigi uses several "ontologies" run as separate background processes to do the indexing -- one "ontology" for each type of indexing being done -- file names, pictures, audio files, etc -- so you'd think this would be a single background process searching the disk, but no it's like 5 or 6. And the thing is, I have no reason to use either of these services. To even find out what these services can do isn't easy, because the documentation for them in the KDE manual is terrible. However if you search around the 'net you'll eventually find this:
As you read the above document here's some details to keep in mind: I use Krusader as my chosen file manager, not Dolphin. I don't use DigiKam or Gwenview (I use Geeqie as my chosen picture viewer). I never use the Alt-F2 Krunner menu, and I never give files tags or comments to them. Therefore Nepomuk as it stands today is totally doesn't serve a purpose for me.
But above all else, I don't want KDE4 choosing on its own when to run a super I/O intensive indexing process just to create a *cache* of things it finds and hold all of that in a huge database. To me that harks back to the 'mlocate' package -- if you've ever been working on a server that suddenly ran like shit and you found an 'updatedb' process running when you viewed the output of 'top', that's the package that did that. But unlike the mlocate package that called the updatedb process via cron, there's no way to tell KDE4 when to allow it to do the indexing or to limit CPU or I/O -- the only thing you can limit is how much RAM is used, which doesn't address this problem. The indexing starts by default, immediately after your very first login, causing the computer to run like utter shit, and your only choice to stop it is to immediately go to System Settings -> Workspace Appearance and Behavior -> Desktop Search and turn these features off . And that's only if you know where to go and what to do. This is why many users that try KDE4 for the first time say "I can't use this, it makes my computer run like shit." And unfortunately, by the default settings KDE4 gives you, they're right.
There are many other levels of FAIL here, too -- the listing of Control Center modules in the KDE Help are not even in alphabetical order, so even if you somehow know that settings for Nepomuk are in the "Desktop Search" section, it's still an effort to find in the list. Then once you look through the help for the Desktop Search, the documentation that is there is simplistic and doesn't even tell you how you can use it, and doesn't give you any warning whatsoever of the performance impact these services have. [I discussed the lack of performance warning with the KDE4 developers at the time, and they were again unsympathetic. After about a week of arguing and "talk to the hand", they told me to create a KDE account and to propose wording myself, which they'd then review and consider. The problem with this suggestion is that they had already made it quite clear that they were not going to take it seriously.] And the way you get into trying to fix the performance disaster is finding several 'nepomuk' processes, so you try to find out how to turn it off in the KDE4 Help, and the Nepomuk entry in the Alphabetical listing doesn't even mention the "Desktop Search" area, so you end up having to search the internet for answers.
As you can probably tell -- I very much love KDE 4.8, which is why this particular subject makes me seethe. KDE4 shines today without these services active, so it really bothers me that the KDE developers make this performance hog active by default, because it's turning people away that would otherwise be able to enjoy KDE4. :-(
Have you tried Razor-qt? That too is a Qt based DE, but w/ fewer bells & whistles - it is to KDE what LXDE is to Gnome.
Huh! No I haven't -- first I've heard of Razor-qt. Unfortunately it's packaged specifically for Ubuntu but not Debian. I had a look at the packages for Precise, but the dependencies are specific to Ubuntu Qt versions and so I can't load these on Debian.
When I find a way, I'll try to check out Razor-qt. Thanks for letting me know about it.