Mount error after power outage

Question

Last night we had a power outage. When I restarted my server this morning I got a error message telling me that a disk failed to mount. Got the option to skip mounting and continue booting. Now when I try to mount the disk (media disk, not a system disk) I get this error:

Error mounting system-managed device /dev/sda2:
Command-line `mount "/mnt/sda2"' exited with non-zero exit status 13: ntfs_mst_post_read_fixup_warn: magic: 0x04e2adc6 size: 4096 usa_ofs: 16595 usa_count: 25841: Invalid argument Actual VCN (0x103f339f56a78da1) of index buffer is different from expected VCN (0x3).
Failed to mount '/dev/sda2': Input/output error NTFS is either inconsistent, or there is a hardware fault, or it's a SoftRAID/FakeRAID hardware.
In the first case run chkdsk /f on Windows then reboot into Windows twice. The usage of the /f parameter is very important!
If the device is a SoftRAID/FakeRAID then first activate it and mount a different device under the /dev/mapper/ directory, (e.g. /dev/mapper/nvidia_eahaabcc1).
Please see the 'dmraid' documentation for more details. (udisks-error-quark)

Is there anyone that can give me some assistance?
I would hate loosing 2 GB of my media files.

Answer 1

When you mount a partition a a flag is set indicating that the volume is in use and that it may not be 'clean'. (As in, things could have been partially changed, leaving other parts 'to be done' before everything is back in a consistent state).

When you unmount a disk buffers are flushed, filesystem administration is all done and a flag is set to indicate a 'clean' state`.

Obviously this does not happen then the power fails.

So upon the next boot your OS detects that the filesystem is in a dirty state and might not be consistent. Usually it will offer to check the filesystem for faults (fsck). If none are found the partition can be mounted as normal. If some are found the user can be asked for input.

With NTFS this is a bit harder because Microsoft does not tell the world how NTFS works. Instead it was reverse engineered. Fixing an unclean NTFS partition is therefor left to the windows tools. This is why you get told to boot windows and to run chkdsk /f.

So, basically:

• Boot windows (either as dual boot, or from a CD/DVD. E.g. from ERD commander).
• Run fsck

If you want to prevent that in the future:

• Either mount the volume read-only by editing /etc/fstab and add ,ro to the mount options.
  E.g. /dev/sda2 /mnt/media ntfs defaults 0 2
• Or prevent power failures. (UPS!)