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

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!


I've included my multipath.conf as well as output from multipath -ll below:


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

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