[Bug 1641124] [NEW] Default failback value is badly chosen

[Jon Skarpeteig]

Public bug reported:

As described by:

https://help.ubuntu.com/lts/serverguide/multipath-setting-up-dm-
multipath.html

The default value for failback is set to manual, instead of immediate.
This effectively breaks the idea of multipath, which allows for
upgrading E.G SAN A side, then upgrade B side when A is complete.

With this set to manual, the system effectively halts. With a system
containing 4 paths to a block device, you'll see this in logs during SAN
firmware upgrade:

November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-4/target0:0:3/0:0:3:0/block/sde and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-4/target0:0:3/0:0:3:0/block/sde and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:03.0/0000:08:00.0/host7/rport-7:0-1/target7:0:0/7:0:0:0/block/sdc and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
November 11th 2016, 13:58:05.000	4	kernel	[585264.496735] sd 0:0:1:0: Asymmetric access state changed
November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:03.0/0000:08:00.0/host7/rport-7:0-1/target7:0:0/7:0:0:0/block/sdc and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:03.0/0000:08:00.0/host7/rport-7:0-1/target7:0:0/7:0:0:0/block/sdc and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:03.0/0000:08:00.0/host7/rport-7:0-1/target7:0:0/7:0:0:0/block/sdc and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda


With the end result that the filesystem is no longer available. If the root partition is on a multipath device (SAN device), then /bin etc. are gone.

Suggested fix: Set failback to immediate as default value

This would ensure that what you would expect to happen, actually happens
- which is when you upgrade SAN firmware, machines continue running like
nothing happened due to redundant paths

** Affects: multipath-tools (Ubuntu)
     Importance: Undecided
         Status: New

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to multipath-tools in Ubuntu.
https://bugs.launchpad.net/bugs/1641124

Title:
  Default failback value is badly chosen

Status in multipath-tools package in Ubuntu:
  New

Bug description:
  As described by:

  https://help.ubuntu.com/lts/serverguide/multipath-setting-up-dm-
  multipath.html

  The default value for failback is set to manual, instead of immediate.
  This effectively breaks the idea of multipath, which allows for
  upgrading E.G SAN A side, then upgrade B side when A is complete.

  With this set to manual, the system effectively halts. With a system
  containing 4 paths to a block device, you'll see this in logs during
  SAN firmware upgrade:

  November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-4/target0:0:3/0:0:3:0/block/sde and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
  November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-4/target0:0:3/0:0:3:0/block/sde and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
  November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:03.0/0000:08:00.0/host7/rport-7:0-1/target7:0:0/7:0:0:0/block/sdc and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
  November 11th 2016, 13:58:05.000	4	kernel	[585264.496735] sd 0:0:1:0: Asymmetric access state changed
  November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-scsi\x2d3600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:03.0/0000:08:00.0/host7/rport-7:0-1/target7:0:0/7:0:0:0/block/sdc and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
  November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:03.0/0000:08:00.0/host7/rport-7:0-1/target7:0:0/7:0:0:0/block/sdc and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda
  November 11th 2016, 13:58:05.000	3	systemd	dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device: Dev dev-disk-by\x2did-wwn\x2d0x600a098038303731702b486638665456.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:03.0/0000:08:00.0/host7/rport-7:0-1/target7:0:0/7:0:0:0/block/sdc and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/0000:04:02.0/0000:07:00.0/host0/rport-0:0-2/target0:0:1/0:0:1:0/block/sda

  
  With the end result that the filesystem is no longer available. If the root partition is on a multipath device (SAN device), then /bin etc. are gone.

  Suggested fix: Set failback to immediate as default value

  This would ensure that what you would expect to happen, actually
  happens - which is when you upgrade SAN firmware, machines continue
  running like nothing happened due to redundant paths

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/multipath-tools/+bug/1641124/+subscriptions