I have a self made fusion drive on a 2009 iMac using a 256gb ssd and a 3tb hard drive. After the 10.8.3 update yesterday I tried to create a bootcamp partition but unfortunately it failed after hours. I had a look at the hard drive manager and the bootcamp partition (I've set it to 303gb) was already there. After having a closer look i noticed that the partition was in the middle of a 1.7 tb partition which was now used for the fusion drive and a 800gb partition that wasn't used anymore. It looks like the bootcamp assistant failed while moving the partition around on the drive.

I started the assistant again to make him remove the partition again which I did but still left the hard drive split into two parts - the 800gb part is still unused and unusable.

Here is what diskutil cs list says:

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Does anyone have a hint for me how I can merge these 800gb part into my fusion drive again?


The surefire fix is to format everything and recreate your Fusion Drive, then restore from a backup.

Hopefully someone can help us fix this another way, but my research shows that non-destructively merging content onto a live fusion drive isn't supported by Apple or another tool chain yet.

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Yes it can be done. I too had this happen. Hopefully you have a back up. If not, and if you can access your files on the remaining partition, then copy those to an external drive, and try the following:

1 open disk utility and select the logical volume and try to repair it. If it gives the option to fix it, you are in luck.

If not, then you can split the logical volume group, and recreate it in terminal. There is a document on the web valled "core storage training" that will guide you through this process. Grab the pdf and read it.

These processes are destructive - meaning all data will be lost, and the drives repartitioned and regrouped. Always have an up to date backup handy.

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