[LU-5758] enabling avoid_asym_router_failure prvents the bring up of ORNL production systems

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Affects Version/s: Lustre 2.4.3, Lustre 2.5.3
• Labels: soak
• Environment: Any 2.4/2.5 clients running against 2.4.3 or 2.5.3 servers.

Epic/Theme

ORNL

• Severity: 3
• Assignee: Liang Zhen (Inactive)
• Reporter: James A Simmons

Description

With the deployment of Lustre 2.5 center wide at ORNL we encountered problems being up the production system due to avoid_sym_router_failure
being enabled by default. The LNET fabric would fail to come up when enabled. Once it was turned off by default everything returned to normal. This would a useful feature at have for this scale of a system. This problem can be easily reproduced at smaller scale in both non-FGR and FGR set ups.

Issue Links

• is related to: LU-6060 ARF doesn't detect lack of interface on a router
• is related to: LU-5485 first mount always fail with avoid_asym_router_failure

Comments

[Peter Jones]

Great - thanks James

[James A Simmons]

No problems. We have been running ARF for months now. You can close this ticket.

[Jian Yu]

Hi James,
Does the ARF issue still exist? If no, can we close this ticket as resolved?

[Liang Zhen (Inactive)]

it's ok to mix them, in that case client/server just can't find out failed remote NI on routers.

[Jian Yu]

Hi Liang,
With the two LNet patches you mentioned above, ORNL tested ARF on a small scale cluster and found it worked. They are going to test it on a large scale cluster.

Now, they have a question about ARF:
"Does this need to be completely on or completely off, or is it possible to have some clusters have it enabled and not others?"

Hi James,
Could you please explain more in case I did not describe the question clearly? Thank you.

[Liang Zhen (Inactive)]

Hi James, because there are many discussions already, I think we should summarise where we are now, please check and correct me if I'm wrong or missed something :

• there are two LNet patches in your environment
  • http://review.whamcloud.com/#/c/12435 (LU-5485 lnet: peer aliveness status and NI status)
  • http://review.whamcloud.com/#/c/13162 (LU-6060 lnet: set downis to 1 if there's no NI for remote net)
• both patches are applied to all nodes (client, server and router)
• If there is any other LNet patch, could you post link of patches, or tarball of lnet.
• ARF can't detect unplugged IB interface on router with above changes
  • in the comment posted at 31/Dec/14 8:59 AM click here , we found router status on client is wrong while unplugging IB interface facing server. But router status on server is correct after unplugging IB interface facing client.
• This problem could either because router can't set NI status to "DOWN" for unknown reason, or because client/server record wrong NI status for router by mistake. To find out which one is the real reason, first we need to check NI status on router after unplugging NI. Because it will take a few minutes for LNet to detect and mark a NI as down, so we need to sample /proc/sys/lnet/nis for 5 minutes, and sample once per 10 seconds.
  • if NI status stays UP forever, then we know router has defect and it can't change NI status.
  • if NI status turns to DOWN, it's probably a bug on non-router node, could you check /proc/sys/lnet/routes and /proc/sys/lnet/routers on client and server.
• we also need to know these values in your environment:
  • live_router_check_interval
  • live_router_check_interval
  • router_ping_timeout

I also have another question:

• The "unplugging IB interface" at here has any difference with the experiment for LU-6060?

Isaac,do you have any advice or insight on this issue?