NVidia ION and /dev/mapper/nvidia_... issues

"I think your problem has more to do with dmraid than LVM (see this note about a similar problem).

dmraid is the Linux fakeRAID facility. It and LVM (and MD RAID, Linux's software RAID facility) use /dev/mapper devices, but as far as I know, LVM requires a standard partition on the disk to use as a physical volume (PV). /dev/mapper/nvidia_* probably refers to a fakeRAID set on an NVidia chipset (using the sata_nv kernel module).

Under this theory, what's happening is that your kernel is detecting the presence of that old RAID metadata on the drives and auto-configuring the device mapper (via dmraid) to use them. If it was LVM, I think you'd be able to tell with fdisk -l /dev/sda.

If your goal is to get back to a plain-jane /dev/sda style disk access, you'll need to:

Verify that DMraid or LVM are in use.

DMraid: try dmraid -s or dmraid -r
LVM: try pvscan or vgscan (?)
You should also try dmsetup ls to query the device mapper directly.

If one or the other are in use, use those configuration tools to remove them.

DMraid: not sure. You can deactivate RAID sets with dmraid -an but this may not be enough. The manpage suggests dmraid -r -E can erase metadata, so that might be necessary.
LVM: pvremove or vgremove (or both)
You might also need to run dmsetup remove or dmsetup remove_all to delete devices from the device mapper driver.

??

In short, you may have to play with the dmraid, dmsetup and various LVM commands to see why your system insists on activating the device mapper. lsmod might be helpful to identify kernel modules in use so you can shut them down if necessary.

See also:

dmraid(8) and dmsetup(8) manpages
See this message for a look at RAID and LVM /dev/mapper devices. Not terribly relevant, but good context, and shows real-world use of dmraid commands."