Disk utility and diskutil information doesn't match.

Question

I'm trying to figure out the layout on one of my mac's. I've been doing unix for about 20 years,
but have only just recently started using MAC OS.
$ diskutil list
/dev/disk0
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *320.1 GB   disk0
1:                        EFI                         209.7 MB   disk0s1
2:                  Apple_HFS Macintosh HD            319.7 GB   disk0s2
/dev/disk1
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:     Apple_partition_scheme                        *639.5 GB   disk1
1:        Apple_partition_map                         32.3 KB    disk1s1
2:                  Apple_HFS afekigjkh2              639.5 GB   disk1s2
/dev/disk2
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:     FDisk_partition_scheme                        *500.1 GB   disk2
1:                  Apple_HFS Untitled                194.4 GB   disk2s1
2:                  Apple_HFS mac_spare               305.7 GB   disk2s5
$ df -h
Filesystem      Size   Used  Avail Capacity  Mounted on
/dev/disk0s2   298Gi  158Gi  139Gi    54%    /
devfs          111Ki  111Ki    0Bi   100%    /dev
map -hosts       0Bi    0Bi    0Bi   100%    /net
map auto_home    0Bi    0Bi    0Bi   100%    /home
/dev/disk1s2   596Gi  456Gi  139Gi    77%    /Users/aftst
/dev/disk2s1   181Gi  288Mi  181Gi     1%    /Volumes/Untitled
/dev/disk2s5   285Gi   29Gi  256Gi    11%    /Volumes/mac_spare
According to CLI, there are 3 disks.
According to the Disk Utility GUI,
there are 2 Disks. The first disk has
1 partition, the 2nd disk has 2 partitions.
The 320gb disk in the GUI is /dev/disk0
The 500gb disk in the GUI is /dev/disk2.
Where is /dev/disk1?

Answer 1

Started using Apple's in 1985, but never ran or studied UNIX.
For one 500 GB Internal HDD and one 500 GB FireWire External HD I get.
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            499.1 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS Mavericks Backup        499.8 GB   disk1s2
I have a half dozen other External HDs, but have them ejected and shut off or disconnected so as not to confuse the information presented above.
To be honest, I'm not sure where or what the 640 GB dev/disk1 is. Although it looks like maybe because of it's Map Scheme, it is either from an old PPC system or perhaps just Partitioned incorrectly for an Intel Mac...?
What disk cloner did you use, generally CarbonCopyCloner (which I use) and SuperDuper bless the External Hard Drive with the proper Partition Map to make a bootable clone...?
As for changing the Partition Scheme, repartitioning with Disk Utility (if it can find that drive) will wipe it clean. Although if it is just a clone, then maybe the best thing to do is start over with the correct Map Scheme and Format. Then use CarbonCopyCloner or SuperDuper to create and maintain your backup drive.