You should really be using the LNET Self Test (LST) to do network testing. You can do this without changing the Lustre config at all.
Cheers, Andreas On 2010-05-20, at 8:43, "Brian J. Murrell" <[email protected]> wrote: > On Thu, 2010-05-20 at 16:27 +0200, Olivier Hargoaa wrote: >> >> 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. > > Without having any other information other than your statement that > "performance is good in one direction but not the other" I wonder why > you consider the network as being the most likely candidate as a > culprit > for this problem. I haven't come across very many networks that > (weren't designed to be and yet) are fast in one direction and slow in > the other. > >> 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. > > Sounds like a lot of rigmarole to test something that I would consider > to be of low probability (given the brief amount of information you > have > provided). But even if I did suspect the network were slow in only > one > direction, before I started mucking with reconfiguring Lustre for > different networks, I would do some basic network throughput testing > to > verify my hypothesis and adjust the probability of the network being > the > problem accordingly. > > Did you do any hardware profiling (i.e. using the lustre-iokit) before > deploying Lustre on this hardware? We always recommend profiling the > hardware for exactly this reason: explaining performance problems. > > Unfortunately, now that you have data on the hardware, it's much more > difficult to profile the hardware because to do it properly, you > need to > be able to write to the disks. > > b. > > _______________________________________________ > Lustre-discuss mailing list > [email protected] > http://lists.lustre.org/mailman/listinfo/lustre-discuss _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
