I am curious what the difference between device-mapper and udev is. I had a post I made earlier where I thought when I updated to KDE4 something happened that was causing troubles mounting an external and secondary hard drive. I now have determined that it appears to be device-mapper. I downloaded the dmsetup utility a while back and when I type dmsetup ls I get:
[root@localhost /]# dmsetup ls
1WD_6400AAK_External (253, 0)
1WD_6400AAK_Externalp1 (253, 1)
SATA_WDC_WD2000JD-22WD-WCAL73024837 (253, 2)
and if I try to mount the drives or access them through Dolphin I get a message that the drives are busy or already mounted. If I enter dmsetup remove_all, this problem disappears. What is the purpose of device-mapper? Is there a way to remove device-mapper or a way to stop device-mapper from mapping my drives? From what it appears, device-mapper is having problems mapping the drives but udev is able to map and mount the drives.