[dm-devel] Question regarding failback option in multipath.conf

[John Brier]

On 09/30/2009 12:41 PM, Eli Klein wrote:
> I'm running into an issue where the failback option in multipath.conf is
> being ignored. I've tried to set this to a value > 0 to cause dm to
> pause before reinstating a recovered path, but it reinstates the path
> immediately. The same is true when setting the value to "manual", the
> path is reinstated immediately. The delay is most useful when a ethernet
> switch has failed or rebooted. During the boot of the switch, the
> interface comes up and drops again multiple times. I'd love to be able
> to introduce a delay before DM marks the path as reinstated after a
> recovery. This would save me the hassle of running into I/O errors (and
> occasional filesystem RO) as the path bounces while the switch is booting.
>
> Thanks in advance for any help or suggestions!
>
> -Eli
>
> I've included my multipath.conf as well as output from multipath -ll below:
>
> multipath.conf:
>
> blacklist {
> devnode "sda$"
> # devnode "*"
> }
>
> ## By default, devices with vendor = "IBM" and product = "S/390.*" are
> ## blacklisted. To enable mulitpathing on these devies, uncomment the
> ## following lines.
> #blacklist_exceptions {
> # device {
> # vendor "IBM"
> # product "S/390.*"
> # }
> #}
>
> ## Use user friendly names, instead of using WWIDs as names.
> defaults {
> user_friendly_names yes
> }
> ##
> ## Here is an example of how to configure some standard options.
> ##
> #
> defaults {
> udev_dir /dev
> polling_interval 10
> selector "round-robin 0"
> path_grouping_policy multibus
> getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
> prio_callout /bin/true
> path_checker readsector0
> rr_min_io 10
> rr_weight priorities
> failback 120
> features "1 queue_if_no_path"
> no_path_retry 1
> user_friendly_name yes
> }

It looks like you have two defaults {} sections. Is that allowed? 
Maybe multipath is only picking up the first one? I'd remove the first 
one/comment out and put user_friendly_names yes in the second one.

Also I think multipath -v3 -d will show you what settings would be 
applied so you don't have to test the behavior by cycling your 
ethernet switch.

For example on one of my systems multipath -v3 shows
mpath1: pgfailback = -2 (controller setting)


After you have it configured right run multipath -v3 without the -d 
(dry run)

Can someone confirm if pgfailback from multipath -v3 output indicates 
the current setting of failback that multipath is using?

John Brier