Disk Utility is saying that I have twice as much storage as I do, causing partitioning problems
I don't know the history of your iMac but your internal hard drive is pretty messed up.

The drive is partitioned to five slices:


the EFI partition at index 1 with a size of 209 MB
a Physical Volume at index 2 with a size of 2.2 TB
a Recovery HD partition at index 3 with a size of 650 MB
a Physical Volume at index 4 with a size of 801 GB
a Boot OS X partition at index 5 with a size of 134 MB


Additionally the device contains a Logical Volume Group (CoreStorage). CoreStorage is a logical volume manager, which is an additional layer between device/partition and a volume.

A Logical Volume Group is based on one or several Physical Volumes (which can be one or several physical devices/partitions) and may contain one or several Logical Volume Families/Logical Volumes.


On one disk the common layout of a LVG is: LVG &lt; one PV (disk0s2) > one LVF > one LV (disk1).
On two disks (e.g a Fusion Drive) the common layout of a LVG is:  LVG &lt; two PVs (disk0s2 &amp; disk1s2) > one LVF > one LV (disk2).


Your actual disk (disk0) has a non-standard layout: LVG &lt; two PVs (disk0s2 &amp; disk0s4) > one LVF > one LV (disk1). This may happen after resizing the CoreStorage stack and adding an additional partition in the then unallocated disk space, formatting it as HFS volume and adding it as a second Physical Volume to the already existing Logical Volume Group.

I can't really explain the origin of the Boot OS X volume (disk0s5).



To salvage the mess, backup Macintosh HD with Time Machine, boot to Internet Recovery Mode, repartition the internal drive to one (main) non-CoreStorage partition and restore the backup:


Booted to your main volume attach your Time Machine backup drive. Go to the menubar and initiate another Time Machine backup cycle by choosing "Backup now...".
Detach the Time Machine drive after the backup is done
Restart to Internet Recovery Mode by pressing alt cmd R at startup.
The prerequisites are the latest firmware update installed, either ethernet or WLAN (WPA/WPA2) and a router with DHCP activated.
On a 50 Mbps-line it takes about 4 min (presenting a small animated globe) to boot to a recovery netboot image which usually is loaded from an apple/akamai server.

I recommend ethernet because it's more reliable. If you are restricted to WIFI and the boot process fails, just restart your Mac until you succeed booting.

Alternatively you may start from a bootable installer thumb drive (Yosemite or El Capitan) or a thumb drive containing a full system (Yosemite or El Capitan).
Open in the menubar Utilities/Terminal
Enter diskutil cs list
You will get an identical output as in your question
enter diskutil cs delete lvgUUID (with lvgUUID: the UUID of your Logical Volume Group). In your case that's diskutil cs delete D60F9C59-F78F-4DA6-A77E-BFCBAA1CCDE7.

The command should delete all CoreStorage items.
Enter exit in Terminal
In the main Recovery Mode Window open "Disk Utility"
Choose the main disk (not one of the volumes!) and hit the Erase button.
Repartition the main disk to 1 partition, OS X Extended (Journaled) and GUID partition map.
Attach your external Time machine backup drive
Quit "Disk Utility" and open "Restore from Time Machine". Choose the external drive as backup source and restore the latest Time Machine backup on your empty internal drive.
After restoring the backup, quit all apps and reboot to your main drive.