Time machine not backing up

Help! Right now, TM is stuck at '20.1 MB of 2.42GB'. I have this setup currently:

An SSD in an Optibay and a HDD in the original slot. The HDD has 3 partitions, one for a CCC clone of the SSD, one for my large data and one for a local time machine.

Last night, I plugged in my external 1TB TM disk while it was still backing up to the internal one: note that it also faced this problem. It finally backed up *111MB* after a few hours.

As I type this, it's probably been stuck at 20.1MB for an hour or so. What's going on? Using iStatMenu I don't see *any* disk activity involving reading from the SSD or writing to my TM.

Another, minorly related problem: I keep getting random *writes* to my SSD, even if the system is idle. It involves spikes of IO, ranging from 8KB/s to 32KB/s. I already have a RAMDisk to minimise these cache writes to the SSD, but apparently it isn't working. Is there a way to see which process is writing to the SSD?