Ansible Role: Multipath

This role will install and configure multipath(d).

The 'multipath' tool is used to detect and coalesce multiple paths to devices, for fail-over or performance reasons.

The 'multipathd' daemon is in charge of checking for failed paths and reconfiguring the affected multipath map when a failure occurs. For this it executes the multipath tool, which in turn will signal multipathd when it is done.

Requirements

This role has to be executed as user 'root'.

Variables

Variable	Type	Required	Default	Comment
multipath_user_friendly_names	bool	No	false	Use the multipath bindings file to assign alias to multipath instead of WWID
multipath_blacklist_wwids	list()	No	N/A	Devices to exclude from multipath topology discovery
multipath_devices	list()	No	N/A	Device-specifc settings

Multipath devices

# INFO: repeat_count syslog issue: https://access.redhat.com/solutions/3484411
# INFO: Test tur with: sg_turs -vvvt -n 4 /dev/sdX
base_multipath_devices:
  - |
    vendor "SYNOLOGY"
    product "Storage"
    path_grouping_policy "multibus"
    path_selector "round-robin 0"
    path_checker "tur"
    prio "alua"
    failback immediate
    no_path_retry "fail"
    flush_on_last_del "yes"

Multipath blacklist

Following command can be used to find the WWID of all devices:

$ multipathd show paths raw format "%d %w"
sda ST1000DM010-2EP102_ZN1YZ1Y8
sdb 360014052bd202b2da441d4299da1ead7
sdc 360014052bd202b2da441d4299da1ead7

All non multipath devices can be added to the blacklist:

multipath_blacklist_wwid:
  - ST1000DM010-2EP102_ZN1YZ1Y8

Note: Once a device is blacklisted it will not show up in the multipath command anymore.

Management

Multipathd

The multipathd command line tool can be used to check the multipath path, devices and blacklist status.

$ multipathd show paths
hcil    dev dev_t pri dm_st  chk_st dev_st  next_check      
8:0:0:1 sdb 8:16  50  active ready  running XXXXXXXXX. 19/20
9:0:0:1 sdc 8:32  50  active ready  running XXXXXXXXX. 19/20

$ multipathd show devices
available block devices:
    sda devnode whitelisted, unmonitored
    sda1 devnode whitelisted, unmonitored
    sda2 devnode whitelisted, unmonitored
    sda3 devnode whitelisted, unmonitored
    sda4 devnode whitelisted, unmonitored
    sdb  devnode whitelisted, monitored
    sdc  devnode whitelisted, monitored
    dm-0 devnode blacklisted, unmonitored
    dm-1 devnode blacklisted, unmonitored
    dm-2 devnode blacklisted, unmonitored
    dm-3 devnode blacklisted, unmonitored
    dm-4 devnode blacklisted, unmonitored
    dm-5 devnode blacklisted, unmonitored
    dm-6 devnode blacklisted, unmonitored

$ multipathd show blacklist
device node rules:
- blacklist:
        (default rule)     !^(sd[a-z]|dasd[a-z]|nvme[0-9])
- exceptions:
        <empty>
udev property rules:
- blacklist:
        <empty>
- exceptions:
        <empty>
protocol rules:
- blacklist:
        <empty>
- exceptions:
        <empty>
wwid rules:
- blacklist:
        (config file rule) ST1000DM010-2EP102_ZN1YZ1Y8
- exceptions:
        <empty>
device rules:
- blacklist:
        (default rule)     SGI:Universal Xport
        (default rule)     ^DGC:LUNZ
        (default rule)     EMC:LUNZ
        (default rule)     DELL:Universal Xport
        (default rule)     FUJITSU:Universal Xport
        (default rule)     IBM:Universal Xport
        (default rule)     IBM:S/390
        (default rule)     LENOVO:Universal Xport
        (default rule)     (NETAPP|LSI|ENGENIO):Universal Xport
        (default rule)     STK:Universal Xport
        (default rule)     SUN:Universal Xport
        (default rule)     (Intel|INTEL):VTrak V-LUN
        (default rule)     Promise:VTrak V-LUN
        (default rule)     Promise:Vess V-LUN
- exceptions:
        <empty>

Multipath

The multipath command line tool provides an overview of the current multipath device maps and configuration.

$ multipath -l
360014052bd202b2da441d4299da1ead7 dm-6 SYNOLOGY,Storage
size=1.0T features='0' hwhandler='1 alua' wp=rw
`-+- policy='round-robin 0' prio=0 status=active
  |- 8:0:0:1 sdb 8:16 active undef running
  `- 9:0:0:1 sdc 8:32 active undef running

$ multipath -t
defaults {
...
}
blacklist {
...
}
blacklist_exceptions {
...
}
devices {
...
}
overrides {
...
}