Meaning of LV -missing_<x>_<x> devices

Hi all,

after the extention of a logical volume (mysqld1) a new "ghost" logical volume appeared with a <missing> suffix:

brw-rw---- 1 root disk 253, 38 Feb 15 20:53 vgmysql-mysqld1 brw-rw---- 1 root disk 253, 44 Jun 1 10:21 vgmysql-mysqld1-missing_4_0

Before performing this LV we partitioned and added a new LUN to the existing vgmysql volume group (again, no errors reported).

We did not discovered this strange device immediately (the lvextend command did not reported errors), only after resizing the file system. The ext2fs operation aborted and so we started with investigation.

Commands like vgdisplay reported errors like:

# vgdisplay -s
/dev/mapper/vgmysql-mysqld1-missing_4_0: read failed after 0 of 4096 at 0: Input/output error
"vg00" 132.59 GB [28.78 GB used / 103.81 GB free]
"vgmysql" 811.95 GB [793.00 GB used / 18.95 GB free]

So online resize of the FS failed, we unmounted the LV, extended with (apparent) success the filesystems and lived happy for a few days. Only while a deep corruption of the FS appeared. :-(

A reboot cleaned up the strange "missing" LV, it is no more present.

The point is: what is the meaning of -missing_* device? When are they generated (and why there are no warnings reported?)

thank your for your suggestions,
best regards,

Enrico

That means the lv was extended onto a PV that is no longer online. The missing device is the extents allocated on the missing PV.

You needed to do an fsck after the aborted filesystem resize. I'm suprised the fs resize didn't make you do so. If you did do the fsck, then there are serious problems with your new PV.

Apparently, the new PV went offline between lvextend and resize.

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