Probably your CoreStorage Logical Volume got corrupted!

I recommend to backup your data to an external drive with Time Machine and rebuild the FusionDrive from scratch.

**Time Machine backup**

- To backup your main volume, boot to your main drive
- Attach an external drive. The drive has to be formatted as an HFS+ Journaled volume. Check this with Disk Utility. If necessary repartition the external drive. All data on the drive will be destroyed after repartitioning/formatting it. The drive has to have the size of the volume to back up (or more).
- Usually you will be asked if the external drive should serve as a Time Machine backup drive after plugging it in for the first time. If not, open Time Machine in the *System Preferences* and configure the external drive as Time Machine backup drive.

 [![enter image description here][1]][1]

 Hit *Select Backup Drive* and choose your external drive:

 [![enter image description here][2]][2]

 Turn on Time Machine. The backup will be started after a few minutes and will take some time depending on the size.

**Rebuild Fusion Drive**

- Boot to Internet Recovery Mode by pressing <kbd>alt</kbd><kbd>cmd</kbd><kbd>R</kbd> while starting your Mac.
- Booted to Internet Recovery Mode open Utilities → Terminal in the menubar and enter:  
`diskutil cs list` to get the CoreStorage listing.  
- Copy the Logical Volume UUID, it's the fifth listed.  
- Now delete the Logical Volume with `diskutil cs deleteVolume LVUUID`.  
  In your case that's `diskutil cs deleteVolume E02059A8-E5D4-4DFF-9D0F-49408380838E`
- Copy the Logical Volume Group UUID, it's the first listed in the listing of `diskutil cs list`.  
- Then delete the Logical Volume Group with `diskutil cs delete LVGUUID`.  
  In your case that's `diskutil cs delete BD4DE488-7C63-4FBA-9FAC-9B92CD56EDE4E`  
- Enter exit and quit 'Terminal'
- Open 'Disk Utility'. Enter 'Ignore' if you are asked to fix the drives.
- Choose your SSD and partition it: 1 Partition Mac OS X Extended (Journaled),
 hit the Options button and choose GUID Partiton table and hit OK and Apply.  
 Please check that the size is ~250 GB  
 
 Example:  
 
 ![ssd][3]
- Choose your HDD and partition it: 1 Partition Mac OS X Extended (Journaled),
 hit the Options button and choose GUID Partiton table and hit OK and Apply.  
 Please check that the size is ~1 TB  
 
 Example:  
 
 ![hdd][4]
 
- Quit Disk Utility and open Terminal
- Enter `diskutil list`

 Example (your disk identifiers and sizes are different of course: Your volume SSD probably has the Identifier disk0s2 and the size 250 GB and your volume HDD probably has the Identifier disk1s2 and the size 1.0 TB):
 
 ![diskutil][5]
- Enter `diskutil cs create "Name" IdentifierSSD IdentifierHDD`  
 In your case probably `diskutil cs create "FusionDrive" disk0s2 disk1s2`.  
 
 Copy the resulting LVGUUID
 
 Example: 
 
 ![cscreate][6]

- Enter `diskutil cs CreateVolume LVGUUID jhfs+ "FusionDrive" 100%`.

 Example:
 
 ![lvcreate][7]


- Enter `diskutil cs list`  
 Check the size of your Logical Volume. It should have the size ~1.250 TB
 
 Example:
 
 ![diskcslist][8]

- Quit Terminal
- Open 'Disk Utility' and check your newly created volume for errors
- Quit 'Disk Utility'
- Attach your external Time Machine backup drive or check this [answer][7] if you use NAS or another network share.
- Open 'Restore from Time Machine Backup'
- Choose the appropriate Time Machine backup and restore your system
- Reboot to your restored system.
- Unmount and detach your Time Machine backup drive
- Open 'Terminal' and enter 'diskutil list'
- Check if your 'Recovery HD' is listed.
- If your 'Recovery HD' is missing, usually reinstalling your current system with the latest available system installer (e.g. 'Install OS X Yosemite (10.10.5)' if Yosemite is currently installed) will recreate it without loosing any data.
- After reinstalling the system with the latest available system installer open `App Store` and install the latest security fixes.


  [1]: https://i.sstatic.net/iRSiy.png
  [2]: https://i.sstatic.net/rsYHt.png
  [3]: https://i.sstatic.net/puoay.png
  [4]: https://i.sstatic.net/g2zac.png
  [5]: https://i.sstatic.net/ME7yM.png
  [6]: https://i.sstatic.net/yIrV7.png
  [7]: https://i.sstatic.net/tRBJV.png
  [8]: https://i.sstatic.net/55bIV.png
  [9]: http://apple.stackexchange.com/questions/162544/how-to-restore-system-from-network-drive