Lustre 1.6 Operations Manual

5. You can delete these files with the unlink or munlink command.
# unlink|munlink filename {filename ...}
Note – There is no functional difference between the unlink and munlink
commands. The unlink command is for newer Linux distributions. You can run the
munlink command if unlink is not available.
When you run the unlink or munlink command, the file on the MDS is
permanently removed.
6. If you need to know, specifically, which parts of the file are missing data, then
you first need to determine the file layout (striping pattern), which includes
the index of the missing OST). Run:
# lfs getstripe -v {filename}
7. Use this computation is to determine which offsets in the file are affected:
[(C*N + X)*S, (C*N + X)*S + S - 1], N = { 0, 1, 2, ...}
where:
C = stripe count
S = stripe size
X = index of bad OST for this file
For example, for a file with 2 stripes, stripe size = 1M, bad OST is at index 0, then
you would have holes in your file at: [(2*N + 0)*1M, (2*N + 0)*1M + 1M - 1], N = { 0,
1, 2, ...}
If the filesystem cannot be mounted, currently there is no way that parses metadata
directly from an MDS. If the bad OST does not start, options to mount the filesystem
are to provide a loop device OST in its place or replace it with a newly-formatted
OST. In that case, the missing objects are created and are read as zero-filled.
In Lustre 1.6 you can mount a filesystem with a missing OST.
Chapter 22 Lustre Troubleshooting Tips 22-7