Lustre 1.6 Operations Manual

Filesystem refuses to mount because of UUID mismatch
When Lustre exports a device for the first time on a target (MDS or OST), it writes a
randomly-generated unique identifier (UUID) to the disk from the .xml
configuration file. On subsequent exports of that device, the Lustre code verifies that
the UUID on disk matches the UUID in the .xml configuration file.
This is a safety feature which avoids many potential configuration errors, such as
devices being renamed after the addition of new disks or controller cards to the
system, cabling errors, etc. This results in messages, such as the following, appearing
on the system console, which normally indicates a system configuration error:
af0ac_mds_scratch_2b27fc413e does not match last_rcvd UUID
8a9c5_mds_scratch_8d2422aa88
In some cases, it is possible to get the incorrect UUID in the configuration file, for
example by regenerating the .xml configuration file a second time. In this case, you
must specify the device UUIDs when the configuration file is built with the --ostuuid
or --mdsuuid options to match the original UUIDs instead of generating new ones
each time.
lmc -add ost --node ostnode --lov lov1 --dev /dev/sdc --ostuuid
3dbf8_OST_ostnode_ddd780786b
lmc -add mds --node mdsnode --mds mds_scratch --dev /dev/sdc --mdsuuid
8a9c5_mds_scratch_8d2422aa88
How do I set up multiple Lustre filesystems on the same node?
Assuming you want to have separate filesystems with different mount locations, you
need a dedicated MDS partition and Logical Object Volume (LOV) for each
filesystem. Each LOV requires a dedicated OST(s).
For example, if you have an MDS server node, mds_server, and want to have mount
points /mnt/foo and /mnt/bar, the following lines are an example of the setup
(leaving out the --add net lines):
Two MDS servers using distinct disks:
lmc -m test.xml --add mds --node mds_server --mds foo-mds --group \
foo-mds --fstype ldiskfs --dev /dev/sda
lmc -m test.xml --add mds --node mds_server --mds bar-mds --group \
bar-mds --fstype ldiskfs --dev /dev/sdb
D-6 Lustre 1.6 Operations Manual • September 2008