Lustre 1.6 Operations Manual

4.2.2 More Complex Configurations
In case of NID/node specification (a node is a server box), it may have multiple
NIDs if it has multiple network interfaces. When a node is specified, generally all of
its NIDs must be listed, delimited by commas (,) so other nodes can choose the NID
appropriate to their own network interfaces. When multiple nodes are specified,
they are delimited by a colon (:) or by repeating a keyword (--mgsnode= or --
failnode=). To obtain all NIDs from a node (while LNET is running), run:
lctl list_nids
4.2.2.1 Failover
This example has a combined MGS/MDT failover pair on uml1 and uml2, and a
OST failover pair on uml3 and uml4. There are corresponding Elan addresses on
uml1 and uml2.
uml1> mkfs.lustre --fsname=testfs --mdt --mgs \
--failnode=uml2,2@elan /dev/sda1
uml1> mount -t lustre /dev/sda1 /mnt/test/mdt
uml3> mkfs.lustre --fsname=testfs --ost --failnode=uml4 \
--mgsnode=uml1,1@elan --mgsnode=uml2,2@elan /dev/sdb
uml3> mount -t lustre /dev/sdb /mnt/test/ost0
client> mount -t lustre uml1,1@elan:uml2,2@elan:/testfs /mnt/testfs
uml1> umount /mnt/mdt
uml2> mount -t lustre /dev/sda1 /mnt/test/mdt
uml2> cat /proc/fs/lustre/mds/testfs-MDT0000/recovery_status
Where multiple NIDs are specified, comma-separation (for example, uml2,2@elan)
means that the two NIDs refer to the same host, and that Lustre needs to choose the
"best" one for communication. Colon-separation (for example, uml1:uml2) means
that the two NIDs refer to two different hosts, and should be treated as failover
locations (Lustre tries the first one, and if that fails, it tries the second one.)
Note – If you have an MGS or MDT configured for failover, perform these steps:
1. On the OST, list the NIDs of all MGS nodes at mkfs time.
OST# mkfs.lustre --fsname sunfs --ost --mgsnode=10.0.0.1
--mgsnode=10.0.0.2 /dev/{device}
2. On the client, mount the filesystem.
client# mount -t lustre 10.0.0.1:10.0.0.2:/sunfs /cfs/client/
4-10 Lustre 1.6 Operations Manual • September 2008