backupd process using too much memory, blocking up system (Yosemite)

Hello,

Since I upgraded to Yosemite (maybe even only after I installed 10.10.1) on my Early 2009 17" MacBook Pro, after a while, a process called "backupd" is started, using all available memory, then switching to virtual memory. After a few hours, it can take more than 20 GB of virtual memory, making the MacBook Pro very slow and unresponsive. Killing the process using Activity Monitor (which can take many minutes because of the unresponsiveness) regains the used memory, and almost immediately makes the machine responsive again.

What is this "backupd" doing anyway, are there means to prevent it from running at all or to let it stop using so much memory, or might there be a bug in OS X 10.10.1?

Cheers,

Dirk