iSCSI SAN shows /dev/mapper/UUID's but can't remove them
 

I have a Dell MD3600i that I loaded ovirt images on. Unfortunately the database crashed, and I'm recovering from that. I mounted the SAN and it shows disks in /dev/mapper/. I can't seem to mount them. They do seem to be taking up space. How do I get rid of them?
I'm using Centos 6.4

those disks are really an LVM structure, and device mapper will show the VM disk LVs as block devices because of that.
To clear your storage, you can simply go into MDSM and delete/recreate the volumes you have there.
Or use dd to zero out the first few MBs of the LUNs, so that all metadata is wiped and the hosts will see the LUNs as empty and raw.

Anyhow, is there a reason you didn't have an engine backup?

I thought i did, but i guess I didn't do it right, or they changed the something in the db schema. Not sure. Either way, when I imported it, it was useless to the engine.

I need to remove the orphaned disks, because I keep getting disk full errors when i'm trying to copy data to the SAN. I can see these disks in /dev/mapper (and as dev/dm-##), but they don't show up in an lvscan. I can fdisk -l and see the partitions, but I want them gone to free up disk space. I don't see any volumes in MDSM. Just the single large disk. Ovirt must create its disks within the main large disk.

I did "dmsetup remove" of the disks. They are out of /dev/mapper now. I'll see if that cleans up the disk space.

dd if=/dev/zero of=/dev/mapper/3600xxxxxxxxxxxxx bs=512 count=200000

just make sure the /dev/mapper path to the LUN is correct