[Lustre-discuss] Replacing faulty OSS/OST

Dilger, Andreas andreas.dilger at intel.com
Tue Oct 21 01:16:44 PDT 2014

On 2014/10/21, 1:44 AM, "Jon Tegner" <tegner at foi.se> wrote:

>Hi again,
>We are running lustre 2.5.3 on a small system, consisting of one
>combined MGS/MDT and four combined OSS/OSTs. One of the OSS/OSTs has
>faulty hardware, and need to be replaced. The procedure I plan on using
>is the following.
>1. Deactivate the faulty OSS.
>2. Make a file-level backup of it (not much data on it).
>3. Temporarily deactivate it.
>The manual seems clear on how to perform these steps, what I'm a bit
>uncertain about is how I introduce the replacement machine (which will
>be a complete new one). Are there certain steps I need to take into
>account, e.g., can will it be possible to create the new OST file system
>with the old ost_index?
>4. Once the replacement is up, and its OST activated, the backup should
>be restored. In the manual it is stated that e2label should be used to
>set the file system label (based on the old ost_index in hex as I
>understand it - a bit curious on this point, since I thought that would
>be taken care of "automatically" (I have never done this when creating
>OSTs before).

If you reformat the new OST using:

  mkfs.lustre --ost --index=N {other opts} /dev/XXX

with the same index as is being replaced, then restore the OST backup into
this filesystem, Lustre shouldn't care about the difference.  With new OST
filesystems, you should also backup and restore the xattrs on all the
files as is needed for the MDT filesystem backup/restore process.

Cheers, Andreas
Andreas Dilger

Lustre Software Architect
Intel High Performance Data Division

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