I really thought ext4 was safe now with Mint 8, and the 2.6.31 kernel. I had read the horror stories about lost data with the 2.6.28 kernel, but all sources have been saying we are now safe with 2.6.31, and it's now the default for Mint 8. I really thought it was safe now.
So when I installed Mint 8 I used ext4 for both my / and /home. It ran great up until last week, and then it happened. I sit in my chair, and turn the PC on and I get an error message that my /home partition will not mount. I think this is odd. So I try again and get the same thing. At this point I'm wondering if the UUID somehow got messed up. I boot into the Live CD, and modify fstab to use a label instead. I try booting again, and still get the same error. I try several more ideas, but ultimately nothing I do recovers /home.
I ended disconnecting the hard drive, and installing Mint on another hard drive (now on SATA0) to get my system back up and running. I then connected the original drive back to the PC as a second drive on SATA1. I was able to see all of the partitions except /home. I copied my data off of the drive, and then started experimenting.
Using gparted I was able to see /home, and confirm that there was data on it, but all attempts to mount the partition failed. I tried moving the partiton to another area of the disk, which I was able to do with gparted, but still could not mount it. I then tried copying the partition to yet another area of the disk, which also worked, but still could not mount it. Basically gparted could see the partition, but it's like the partition table forgot how to read the data contained within it.
So at this point I'm still not sure if the partition simply suffered a data failure, or if the hardware itself was failing. I made a boot CD with Western Digital's Data Lifeguard tools to test the drive. With this disk you can run a battery of tests, and to be honest I was really hoping the disk would come up as bad. If it does the software generates an RMA code which you need to put in a warranty claim. Well every test came back just fine. According to every test I ran there is nothing wrong with the drive.
So the bottom line is that the ext4 partition simply failed. At this point I'm back to running my system on ext3, and have no plans to venture back to ext4 anytime soon.