Upon every boot I must do this: dmsetup ls, dmsetup remove...
 

About a year ago I had this issue where a disk wouldn't show up until I did the following:

# dmsetup ls, dmsetup remove ddf1_foobar, dmsetup ls

So this has been a comment in my /etc/fstab since then. I have to follow these steps each time I restart the system. This is a clumbsy workaround though --can someone tell me how I can fix this permanently?

What distro/version of Linux?

You could put those commands in a script and set the script to run on boot. The classical way to do this is to put it in /etc/rc.local (note that rc.local may be in different locations in /etc, depending on the distro.

You might take a look at the log files in /var/log to see whether there is some hint as to what is causing this problem. Look for files named /var/log/messages, /var/log/system and /var/log/boot for starters. You may have to have root privileges to access them.

It might be easiest to view the files with less, since it will enable you to navigate in them.

See man less for details.

Upon further investigation I found some notes from years ago where I first saw this. In short the solution is to uninstall dmraid or append nodmraid to kernel boot options.

http://forums.fedoraforum.org/showthread.php?t=137861

Glad you solved it. Thanks for the update.