Hi, I have an early 2011 15" MBP (2.0GHz). I swapped the DVD drive for an SSD with a tray I bought on eBay (or was it Amazon...). I had my primary boot partition on it. My original HDD was partitioned, one partition as a clone of the SSD and one being the original mac install that came with the computer, I would put my large files there as well but I never removed the Mac OS install from it. So, yesterday, I had lots of programs open as I was finishing up a project and uploading code to my Arduino to wrap thing up. Suddenly, my computer froze. The interface started to become unreactive... I thought the Arduino messed something up so I rebooted my computer. I took a really long time and it ended up booting in the original mac partition. In finder, my SSD was no where to be found... Luckily I had kept that partition in place as I was on a super tight deadline, I downloaded my code off Dropbox and I didn't loose a second of work and I was able to finish every thing. If this can be a lesson to anyone with an optibay system, keep a bootable cloned partition in your secondary drive. It's quite amazing, I just lost 10 minutes total on this. Having a backup is nice but having a backup installed in your computer is even better. Getting back to my problem, as I was restarting my computer today, the drive appeared, it didn't yesterday. However, it seems to be corrupt in some way. As the computer booted up, it told me something along the lines that it found a drive but couldn't do anything with it and opened up Disk Utility. In there, Repair Disk is greyed out. My only option at this time seems to be to erase it. However, I have quite a bit of stuff that hasn't been backed up properly on it, so I'd like to try to recover it. This is what the diskutil command gives me. louis-leblancs-macbook-2:~ louisleblanc$ diskutil list /dev/disk0 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *500.1 GB disk0 1: EFI 209.7 MB disk0s1 2: Apple_HFS Macintosh HD 371.8 GB disk0s2 3: Apple_HFS ssdback 127.9 GB disk0s3 /dev/disk1 #: TYPE NAME SIZE IDENTIFIER 0: FDisk_partition_scheme *128.0 GB disk1 1: 0xEE 128.0 GB disk1s1 louis-leblancs-macbook-2:~ louisleblanc$ diskutil info /dev/disk1 Device Identifier: disk1 Device Node: /dev/disk1 Part Of Whole: disk1 Device / Media Name: M4-CT128M4SSD2 Media Volume Name: Escaped with Unicode: Mounted: No File System: None Partition Type: FDisk_partition_scheme Bootable: Not bootable Media Type: Generic Protocol: SATA SMART Status: Not Supported Total Size: 128.0 GB (128035676160 Bytes) (exactly 250069680 512-Byte-Blocks) Volume Free Space: Not Applicable Read-Only Media: No Read-Only Volume: Not applicable (no filesystem) Ejectable: No Whole: Yes Internal: Yes OS 9 Drivers: No Low Level Format: Not Supported I'll try to see if I have any more luck recovering the files using a Mountain Lion USB key. Next, I'll try a booting with an Ubuntu live USB. I've had some success reading corrupt mac file systems with it that mac os would have none of. Anyone has a suggestion on how to recover this? What do you think caused it? Could it be a bad physical connection? After all the drive wasn't showing up yesterday and now it is. Could it be that it just degraded so badly that it just died on me? I hadn't checked my disk usage but I'm fairly sure there was at least 20GB free on the drive. Though in the past, on a previous install of mac os on the same drive, I know I've got it dangerously close to full like 2 to 4 GB left. Though this doesn't seem likely as I would expect it to degrade the drive rather than lock it up. I'm also suspecting the Arduino might have had something to do with it. It could also have been just mac os being silly and corrupting the filesystem on its own.