We are running lustre-2.3.0 on RHEL6 and today one of our OSS nodes had a kernel crash (within the lustre code). A screen dump after the crash is available here: http://www.gb.nrao.edu/~wbaudler/crash.jpg Nothing was logged on the local or network syslog. After a hard reset it now refuses to mount one of the OSTs (It has 2, the other one is fine). $ mount /export/pulsar/ost81 mount.lustre: /dev/sdb has not been formatted with mkfs.lustre or the backend filesystem type is not supported by this tool No syslog messages from the failed mount command, so this looks pretty severe. I can still mount it as ldiskfs, but there seems to be stuff missing that is usually there when mounting as ldiskfs. A e2fsck dry run didn''t turn up anything, except that lost+found is missing ??? Script started on Fri 09 Aug 2013 01:53:11 PM EDT [root@nadrach ~]$ e2fsck -fn /dev/sdb e2fsck 1.42.3.wc3 (15-Aug-2012) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity /lost+found not found. Create? no Pass 4: Checking reference counts Pass 5: Checking group summary information vegas-OST0051: ********** WARNING: Filesystem still has errors ********** vegas-OST0051: 84724/40054144 files (30.6% non-contiguous), 9572242905/10253849088 blocks I am thinking of making a filesystem level backup of that OST (just in case I have to create a fresh OST and restore), then mount it ldiskfs again and try to fix the OST config somehow. The manual has some hints on how to do this here: http://build.whamcloud.com/job/lustre-manual/lastSuccessfulBuild/artifact/lustre_manual.xhtml#idp4155904 Am I on the right track here? Any help appreciated. Wolfgang