Fix lagging display performance on retina MacBook Pro

This weekend my Mac suddenly started behaving strangely: moving windows around occurred with a nearly psychodelic delay, mission control (aka exposé) was “jerky”, and scrolling was not fun. Forcing the graphics card to the discrete NVIDIA GT 650 instead of integrated Intel GPU sped things up, but the overall experience still didn’t feel right. Since the onset was sudden I immediately though: imminent hardware failure! But thankfully that turned out not to be the case.

Recover a failed TimeMachine backup

I recently received an unpleasant warning message after TimeMachine routinely tried to perform a backup:

Time Machine completed a verification of your backups on “matmos”. To improve reliability, Time Machine must create a new backup for you.
Click Start New Backup to create a new backup. This will remove your existing backup history. This could take several hours.
Click Back Up Later to be reminded tomorrow. Time Machine won’t perform backups during this time.Time Machine completed a verification of your backups on 'matmos'. To improve reliability, Time Machine must create a new backup for you.  Click Start New Backup to create a new backup. This will remove your existing backup history. This could take several hours.  Click Back Up Later to be reminded tomorrow. Time Machine won’t perform backups during this time.