[dm-devel] marginal_path_double_failed_time

[Khitai Pang]

Hi,

I've been trying the new multipath configuration options in RHEL8 beta, the options are listed in https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8-beta/html-single/8.0_beta_release_notes/index#file_systems_and_storage_2.

Below is my multipath configuration:

defaults {
        user_friendly_names yes
        find_multipaths yes
        marginal_path_double_failed_time        120
        marginal_path_err_sample_time           121
        marginal_path_err_rate_threshold        10
        marginal_path_err_recheck_gap_time      30
}

and this is the multipath storage:

3600124f0f822cba90003551f67355d000d dm-2 SUN,ZFS Storage 7120
size=100G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
`-+- policy='service-time 0' prio=50 status=active
  |- 6:0:0:4  sdf  8:80    failed faulty running
  |- 6:0:1:4  sdbv 68:144  failed faulty running
  |- 8:0:0:4  sdab 65:176  active ready running
  `- 8:0:1:4  sdcy 70:96   active ready running

To do the test, I use dd to write to the storage and use "iostat 1" to check IO, then log onto the fc switch to disable a port, after port being disabled, two paths will fail, and IO is only seen on the remaining two paths, then I immediately re-enable the port, and IO will again be seen on all 4 paths, and then I do this path disable and re-enable all over again, but no matter how fast I do this again and again, after re-enabling the fc switch port, the failed paths will always go online again after port re-enable and IO are seen on them.  According to the manpage of multipath.conf: "when a path failed event occurs twice in marginal_path_double_failed_time seconds due to an IO error and all the other three parameters are set, multipathd will fail the path and enqueue this path into a queue...".  Did I get anything wrong?

Thanks!

Regards,
Khitai
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