Ah yes, I see what the lnet unit file is doing.  OK, I think this is all 
straighten out and working great now.  We have a fairly extensive init script 
(the lustre3 script in previous posts) that does various checks in addition to 
loading modules and mounting/unmounting the filesystems.  But at its core, the 
start is now doing this:

   /usr/bin/systemctl start lnet  >& /dev/null
   modprobe lustre
    <mount lustre FS's>

The stop portion does:

    <umount lustre FS's>
    /usr/bin/systemctl stop lnet  >& /dev/null
    /usr/sbin/lustre_rmmod


The final conf files I'm using are:

lnet.conf:

net:
    - net type: o2ib1
      local NI(s):
        - interfaces:
              0: ib0
global:
    discovery: 0



/etc/modprobe.d/lustre.conf:

options ko2iblnd map_on_demand=32



Using the lnet systemd unit file properly loads the configuration and shows 
discovery=0 (without any of lnet stuff in the modprobe conf file).  We could 
properly enable the lnet unit file and make a dependency to make sure our init 
script runs after the lnet service but its a little easier to just run the 
systemctl commands in our init script.

I would be interested if others have a cleaner way to do all mounting, etc. in 
a more native systemd manner.  It probably just involves making a simple unit 
file to run a script.  Probably six of one, half dozen of the other but if 
anyone has experience with the pros and cons, please let me know.

Thanks a ton for the help on this.  Much appreciated.



From: "Horn, Chris" <chris.h...@hpe.com>
Date: Tuesday, September 14, 2021 at 9:40 AM
To: "Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.]" 
<darby.vicke...@nasa.gov>, Riccardo Veraldi <riccardo.vera...@cnaf.infn.it>, 
"lustre-discuss@lists.lustre.org" <lustre-discuss@lists.lustre.org>
Subject: [EXTERNAL] Re: Re: [lustre-discuss] Disabling multi-rail dynamic 
discovery

When you start LNet via ‘modprobe lnet; lctl net up’, that doesn’t load the 
configuration from /etc/lnet.conf. It is going to configure LNet based only on 
kernel module parameters. Since you removed the ‘options lnet networks’ from 
your modprobe.conf file, it is going to use the default configuration which is 
@tcp on whatever the first ethernet interface w/ipv4 configured that it finds.

To load /etc/lnet.conf you can use systemctl start lnet.service (or 
equivalent), or if you want to do it manually:

modprobe lnet
lnetctl lnet configure
lnetctl lnet import < /etc/lnet.conf

Also, I would try this for your lnet.conf

net:
    - net type: o2ib
      local NI(s):
        - interfaces:
              0: ib0
global:
    discovery: 0

Chris Horn

From: Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.] 
<darby.vicke...@nasa.gov>
Date: Tuesday, September 14, 2021 at 10:17 AM
To: Horn, Chris <chris.h...@hpe.com>, Riccardo Veraldi 
<riccardo.vera...@cnaf.infn.it>, lustre-discuss@lists.lustre.org 
<lustre-discuss@lists.lustre.org>
Subject: Re: [EXTERNAL] Re: [lustre-discuss] Disabling multi-rail dynamic 
discovery
So I"m a little confused.

When I take the "options lnet networks=o2ib1(ib0)"  line out of the modprobe 
conf file and instead put that info in the lnet.conf file, things don't work 
properly.

[root@r1i1n18 lnet]# cat /etc/modprobe.d/lustre.conf
options ko2iblnd map_on_demand=32
[root@r1i1n18 lnet]# cat /etc/lnet.conf
ip2nets:
- net-spec: o2ib1
   interfaces:
      0: ib0
global:
    discovery: 0
[root@r1i1n18 lnet]# modprobe lnet
[root@r1i1n18 lnet]# lctl network up
LNET configured
[root@r1i1n18 lnet]# service lustre3 start
Mounting /ephemeral... mount.lustre: mount 
10.150.100.30@o2ib1:10.150.100.31@o2ib1:/scratch/work at /ephemeral failed: No 
such file or directory
Is the MGS specification correct?
Is the filesystem name correct?
If upgrading, is the copied client log valid? (see upgrade docs)
FAILED.
Mounting /nobackup... mount.lustre: mount 
10.150.100.30@o2ib1:10.150.100.31@o2ib1:/hpfs-fsl/work at /nobackup failed: No 
such file or directory
Is the MGS specification correct?
Is the filesystem name correct?
If upgrading, is the copied client log valid? (see upgrade docs)
FAILED.
[root@r1i1n18 lnet]#


The logs when this happens:

Sep 14 09:53:38 r1i1n18 kernel: LNet: Added LNI 
10.159.0.39@tcp<mailto:10.159.0.39@tcp> [8/256/0/180]
Sep 14 09:53:38 r1i1n18 kernel: Lnet: Accept secure, port 988
Sep 14 09:53:54 r1i1n18 kernel: Lustre: Lustre: Build Version: 2.12.6
Sep 14 09:53:55 r1i1n18 kernel: LustreError: 
34174:0:(ldlm_lib.c:494:client_obd_setup()) can't add initial connection
Sep 14 09:53:55 r1i1n18 kernel: LustreError: 
34174:0:(obd_config.c:559:class_setup()) setup 
MGC10.150.100.30@o<mailto:MGC10.150.100.30@o>2ib1 failed (-2)
Sep 14 09:53:55 r1i1n18 kernel: LustreError: 
34174:0:(obd_mount.c:202:lustre_start_simple()) 
MGC10.150.100.30@o<mailto:MGC10.150.100.30@o>2ib1 setup error -2
Sep 14 09:53:55 r1i1n18 kernel: LustreError: 
34174:0:(obd_mount.c:1608:lustre_fill_super()) Unable to mount  (-2)

Note the @tcp above – it looks like without the modprobe conf file, the lnet 
module isn't getting set up properly.  When this happens, I'm not able to shut 
down lnet or unload the kernel modules to try again.  The only way I've been 
able to recover from this is to reboot the node.  If I add the "options lnet" 
stuff back to the modprobe conf file, everything works as expected.  Do I not 
have enough info in lnet.conf or are both just required?

Chris, adding lnet_peer_discovery_disabled=1 to my lnet options does indeed 
seem to work.  Thanks!

Darby


From: "Horn, Chris" <chris.h...@hpe.com>
Date: Monday, September 13, 2021 at 4:59 PM
To: Riccardo Veraldi <riccardo.vera...@cnaf.infn.it>, "Vicker, Darby J. 
(JSC-EG111)[Jacobs Technology, Inc.]" <darby.vicke...@nasa.gov>, 
"lustre-discuss@lists.lustre.org" <lustre-discuss@lists.lustre.org>
Subject: [EXTERNAL] Re: [lustre-discuss] Disabling multi-rail dynamic discovery

I’m not sure why lnetctl import wouldn’t correctly set discovery. Might be a 
bug. You can try setting the kernel module parameter to disable discovery:

options lnet lnet_peer_discovery_disabled=1

This obviously requires LNet to be reloaded.

I would not recommend toggling discovery via the CLI as there are some bugs 
with correctly dealing with the fallout of that (peers going from MR enabled to 
MR disabled).

Chris Horn

From: lustre-discuss <lustre-discuss-boun...@lists.lustre.org> on behalf of 
Riccardo Veraldi <riccardo.vera...@cnaf.infn.it>
Date: Monday, September 13, 2021 at 5:25 PM
To: Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.] 
<darby.vicke...@nasa.gov>, lustre-discuss@lists.lustre.org 
<lustre-discuss@lists.lustre.org>
Subject: Re: [lustre-discuss] Disabling multi-rail dynamic discovery

I supposed you removed the /etc/modprobe.d/lustre.conf completely.

I only have the lnet service enabled at startup, I do not start any lustre3 
service, but I am running lustre 2.12.0 sorry not 2.14

so something might be different.

Did you start over with a clean configuration ?

Did you reboot your system to make sure it picks up the new config ? At least 
for me sometimes the lnet module does not unload correctly.

Also I have to mention in my setup I did disable discovery also on the OSSes 
not only client side.

Generally it is not advisable to disable Multi-rail unless you have backward 
compatibility issues with older lustre peers.

But disabling discovery will also disable Multi-rail.

You can try with

lenetctl set discovery 0

as  you already did,

then you do

lnetctl -b export > /etc/lnet.conf

check discovery is set to 0 in the file and if not edit it and set it to 0.

reboot and see if things changes.

If anyway you did not define any tcp interface in lnet.conf  you should not see 
any tcp peers.


On 9/13/21 2:59 PM, Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.] wrote:
Thanks Rick.  I removed my lnet modprobe options and adapted my lnet.conf file 
to:

# cat /etc/lnet.conf
ip2nets:
- net-spec: o2ib1
   interfaces:
      0: ib0
global:
    discovery: 0
#


Now "lnetctl export" doesn't have any reference to NIDs on the other networks, 
so that's good.  However, I'm still seeing some values that concern me:


# lnetctl export | grep -e Multi -e discover | sort -u
    discovery: 1
      Multi-Rail: True
#

Any idea why discovery is still 1 if I'm specifying that to 0 in the lnet.conf 
file?  I'm a little concerned that with Multi-Rail still True and discovery on, 
the client could still find its way back to the TCP route.


From: Riccardo Veraldi 
<riccardo.vera...@cnaf.infn.it><mailto:riccardo.vera...@cnaf.infn.it>
Date: Monday, September 13, 2021 at 3:16 PM
To: "Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.]" 
<darby.vicke...@nasa.gov><mailto:darby.vicke...@nasa.gov>, 
"lustre-discuss@lists.lustre.org"<mailto:lustre-discuss@lists.lustre.org> 
<lustre-discuss@lists.lustre.org><mailto:lustre-discuss@lists.lustre.org>
Subject: [EXTERNAL] Re: [lustre-discuss] Disabling multi-rail dynamic discovery


I would use configuration on /etc/lnet.conf and I would not use anymore the 
older style configuration in

/etc/modprobe.d/lustre.conf
for example in my /etc/lnet.conf configuration I have:

ip2nets:
 - net-spec: o2ib
   interfaces:
      0: ib0
 - net-spec: tcp
   interfaces:
      0: enp24s0f0
global:
    discovery: 0

As I disabled the auto discovery.

Regarding ko2ib you can just use /etc/modprobe.d/ko2iblnd.conf

Mine looks like this:

options ko2iblnd peer_credits=128 peer_credits_hiw=64 credits=1024 ntx=2048 
map_on_demand=256 fmr_pool_size=2048 fmr_flush_trigger=512 fmr_cache=1 
conns_per_peer=4

Hope it helps.

Rick


On 9/13/21 1:53 PM, Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.] via 
lustre-discuss wrote:
Hello,

I would like to know how to turn off auto discovery of peers on a client.  This 
seems like it should be straight forward but we can't get it to work. Please 
fill me in on what I'm missing.

We recently upgraded our servers to 2.14.  Our servers are multi-homed (1 tcp 
network and 2 separate IB networks) but we want them to be single rail.  On one 
of our clusters we are still using the 2.12.6 client and it uses one of the IB 
networks for lustre.  The modprobe file from one of the client nodes:


# cat /etc/modprobe.d/lustre.conf
options lnet networks=o2ib1(ib0)
options ko2iblnd map_on_demand=32
#


The client does have a route to the TCP network.  This is intended to allow 
jobs on the compute nodes to access licenese servers, not for any serious I/O.  
We recently discovered that due to some instability in the IB fabric, the 
client was trying to fail over to tcp:


# dmesg | grep Lustre
[  250.205912] Lustre: Lustre: Build Version: 2.12.6
[  255.886086] Lustre: Mounted scratch-client
[  287.247547] Lustre: 3472:0:(client.c:2146:ptlrpc_expire_one_request()) @@@ 
Request sent has timed out for sent delay: [sent 1630699139/real 0]  
req@ffff98deb9358480 x1709911947878336/t0(0) 
o9->hpfs-fsl-OST0001-osc-ffff9880cfb80000@192.52.98.33@tcp:28/4<mailto:hpfs-fsl-OST0001-osc-ffff9880cfb80000@192.52.98.33@tcp:28/4>
 lens 224/224 e 0 to 1 dl 1630699145 ref 2 fl Rpc:XN/0/ffffffff rc 0/-1
[  739.832744] Lustre: 3526:0:(client.c:2146:ptlrpc_expire_one_request()) @@@ 
Request sent has timed out for sent delay: [sent 1630699591/real 0]  
req@ffff98deb935da00 x1709911947883520/t0(0) 
o400->scratch-MDT0000-mdc-ffff98b0f1fc0800@192.52.98.31@tcp:12/10<mailto:scratch-MDT0000-mdc-ffff98b0f1fc0800@192.52.98.31@tcp:12/10>
 lens 224/224 e 0 to 1 dl 1630699598 ref 2 fl Rpc:XN/0/ffffffff rc 0/-1
[  739.832755] Lustre: 3526:0:(client.c:2146:ptlrpc_expire_one_request()) 
Skipped 5 previous similar messages
[  739.832762] LustreError: 166-1: MGC10.150.100.30@o2ib1: Connection to MGS 
(at 192.52.98.30@tcp) was lost; in progress operations using this service will 
fail
[  739.832769] Lustre: hpfs-fsl-MDT0000-mdc-ffff9880cfb80000: Connection to 
hpfs-fsl-MDT0000 (at 192.52.98.30@tcp) was lost; in progress operations using 
this service will wait for recovery to complete
[ 1090.978619] LustreError: 167-0: scratch-MDT0000-mdc-ffff98b0f1fc0800: This 
client was evicted by scratch-MDT0000; in progress operations using this 
service will fail.


I'm pretty sure this is due to the auto discovery.  Again, from a client:



# lnetctl export | grep -e Multi -e discover | sort -u

    discovery: 0

      Multi-Rail: True

#


We want to restrict lustre to only the IB NID but its not clear exactly how to 
do that.

Here is one attempt:


[root@r1i1n18 lnet]# service lustre3 stop
Shutting down lustre mounts
Lustre modules successfully unloaded
[root@r1i1n18 lnet]# lsmod | grep lnet
[root@r1i1n18 lnet]# cat /etc/lnet.conf
global:
    discovery: 0
[root@r1i1n18 lnet]# service lustre3 start
Mounting /ephemeral... done.
Mounting /nobackup... done.
[root@r1i1n18 lnet]# lnetctl export | grep -e Multi -e discover | sort -u
    discovery: 1
      Multi-Rail: True
[root@r1i1n18 lnet]#


And a similar attempt (same lnet.conf file), but trying to turn off the 
discovery before doing the mounts:



[root@r1i1n18 lnet]# service lustre3 stop

Shutting down lustre mounts

Lustre modules successfully unloaded

[root@r1i1n18 lnet]# modprobe lnet

[root@r1i1n18 lnet]# lnetctl set discovery 0

[root@r1i1n18 lnet]# service lustre3 start

Mounting /ephemeral... done.

Mounting /nobackup... done.

[root@r1i1n18 lnet]# lnetctl export | grep -e Multi -e discover | sort -u

    discovery: 0

      Multi-Rail: True

[root@r1i1n18 lnet]#

If someone can point me in the right direction, I'd appreciate it.

Thanks,
Darby


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