akonadi in KDE was and is a real pita, as the boundaries within KDE applications such as konversation or kontact are way too much, and decrease performance entirely. disabling akonadi could be a solution (as well as nepomouk and strigii by not wanting an indexed desktop search – see this explaination).

furthermore, there is a bug in current KDE upstream, where disabled akonadi would cause the startup of konversation to be waiting for a timeout on a “migration” – see this bug.

since konversation is one of those applications i like to use with KDE, that behaviour really sucks. so being a badass, re-enabling akonadi could work. debian sid recently changed the backend for akonadi from mysql to sqlite3 which seems to scale a lot better. see this proposal.

install the sqlite backend, and entirely purge the mysql one. be aware of the fact that this causes data loss on all actual savings as the backend gets re-initialized!

$ sudo apt-get install akonadi-backend-sqlite
$ sudo apt-get remove --purge akonadi-backend-mysql

$ rm -rf ~/.config/akonadi/agent*
$ rm -rf ~/.local/share/akonadi
$ rm -rf ~/.kde/share/config/akonadi-firstrunrc

then configure the backend.

$ vim /home/michi/.config/akonadi/akonadiserverrc

[%General]
Driver=QSQLITE3

[QSQLITE3]
Name=/home/michi/.local/share/akonadi/akonadi.db

[Debug]
Tracer=null

start it

$ sudo akonadictl start

Note: you cannot change the akonadi backend via gui currently, so this needs to be done by hand.

Update 17.6.2012: The short version, without being logged into KDE:

# apt-get install akonadi-backend-sqlite
# apt-get remove --purge akonadi-backend-mysql akonadi-backend-postgresql

$ rm -rf ~/.local/share/akonadi ~/.config/akonadi/* ~/.kde/share/config/akonadi-firstrunrc
$ printf "%sn%sn" '[%General]' 'Driver=QSQLITE3' > ~/.config/akonadi/akonadiserverrc