[Lustre-discuss] Modifying Lustre network (good practices)

[Olivier Hargoaa]

Dear All,

We have a cluster with lustre critical data. On this cluster there are 
three networks on each Lustre server and client : one ethernet network 
for administration (eth0), and two other ethernet networks configured in 
bonding (bond0: eth1 & eth2). On Lustre we get poor read performances 
and good write performances so we decide to modify Lustre network in 
order to see if problems comes from network layer.

Currently Lustre network is bond0. We want to set it as eth0, then eth1, 
then eth2 and finally back to bond0 in order to compare performances.

Therefore, we'll perform the following steps: we will umount the 
filesystem, reformat the mgs, change lnet options in modprobe file, 
start new mgs server, and finally modify our ost and mdt with 
tunefs.lustre with failover and mgs new nids using "--erase-params" and 
"--writeconf" options.

We tested it successfully on a test filesystem but we read in the manual 
that this can be really dangerous. Do you agree with this procedure? Do 
you have some advice or practice on this kind of requests? What's the 
danger?

Regards.

-- 
Olivier, Hargoaa
Phone: + 33 4 76 29 76 25