Well, I've done it. I tried to make a boot camp partition under El Capitan. Now, please don't tell me stuff like "It's a beta, what did you expect" - I know this probably wasn't the best idea. Anyway, during the bootcamp setup process, everything went fine until the very end, when it just reported an error and told me to erase the bootcamp partition in Disk Util and try again. So I did. Opened up the new Disk Util, deleted the bootcamp partition - and then OS X refused to merge partitions. It did everything, came to the point where it said "Merging Partitions" and then just wrote "Operation Failed". Now I have two partitions - one is the part of the corestorage and forms the Fusion Drive with the SSD, and the other one is just a separate partition on the HDD. And for some reason it is 750Gb in size, instead of the 200 I had originally set aside for Windows Boot Camp. Here's a screenshot: https://dl.dropboxusercontent.com/u/7671549/Screenshot 2015-06-21 12.56.51.png I tried deleting that new partition and mergeing it (as seen on the image) and it just says Operation Failed. I can use both partitions with no problems, I just can't merge them into one. I also tried to do it from the Recovery mode, it gives the same error message. If this is a bug in El Capitan which will be fixed - I'm fine with waiting for the final release. I don't mind having these two partitions. Also, I did not try to erase the entire logical volume as that would force me to reinstall the OS X. I have a feeling this might help solve the issue, but I'm not sure. Any advice? Thanks.