Linux – Recovering a file with bad blocks in the middle

Filesystem layers in Linux (starting in reverse order, from the physical drive to the filesystem):

1. physical device
   • /dev/sdi
   • /dev/sdj
   • /dev/sdk
   • /dev/sdl

2. special md partition type on each drive (when used)

   • this may or may not be present. While it is recommended that you simply make single partitions on each drive that spans the entire size of the drive it is on, it is possible to specify the entire drive by using the device name directly. Note that this can cause some partition tools to become confused about what they are dealing with (because the partition table simply "goes away"), so I don't recommend it.

   In your case, the entire drives are specified, so there are no partitions to see. You won't have to worry about this.

3. md driver (when used)

   • /dev/md2

   Your output from both the detail and /proc report that the array is up on all drives and no drives are in a failed state. This means the array is healthy!

4. LVM (when used)

   • Type the following into a shell while logged in as root:

   pvscan && vgscan && lvscan

   If there are any volumes to be found, they should be here. Note that the volume scan process is controlled by a file that can choose certain devices to ignore when it performs the scan. You'll want to make sure that you scan /dev/md2 explicitly. Each LVM volume has a GUID imprinted into it; if this is lost or corrupted, it can cause some of the issues you are seeing. The goal here is to get your LVM volumes recognized. Once they are healthy, you'll be in good shape.

5. filesystem

   I think you know the drill here.

From here you should be able to recover your filesystem(s).

The first thing I would do is use ddrescue from a liveCD to make a backup image of the drive. If there's physical damage to the drive, there's a chance that there's a finite amount of time until it fails completely. Then, make a copy of that image to work on.

From there, I have no suggestions that you haven't tried. Others smarter than me will have to help you there.