[Bug 644489] Re: constantly changes /dev/disk/by-id/{scsi, wwn}-* LUN symlinks with multipathing

John Morrissey jwm at horde.net
Mon Jun 20 13:37:23 UTC 2011


On Sat, Jun 18, 2011 at 09:00:59PM -0000, Peter Petrakis wrote:
> Excellent, you're still interested. I've got a fix for you to try.
> Attached is a custom version of mpath_prio_netapp that should
> not generate any more change events for you. Please post
> for comparison that this new version returns the same data
> as the old one.
[snip]
> Once you verify that the updated prio checker no longer
> generates change events, start up multipathd again and
> verify that this continues to be true. Thanks!

Everything seems to be as anticipated:

[jwm at pxe-237.roch.ny:pts/0 ~> sudo apt-get install multipath-tools=0.4.8-14ubuntu4 multipath-tools-boot=0.4.8-14ubuntu4 kpartx=0.4.8-14ubuntu4
[...]
[jwm at pxe-237.roch.ny:pts/0 ~> for i in /dev/sd[abcd]; do sudo mpath_prio_netapp $i; done
4
1
4
1
[jwm at pxe-237.roch.ny:pts/0 ~> sudo apt-get dist-upgrade
[...]
Preparing to replace kpartx 0.4.8-14ubuntu4 (using .../kpartx_0.4.8-14ubuntu5~lp644489_amd64.deb) ...
[...]
Preparing to replace multipath-tools 0.4.8-14ubuntu4 (using .../multipath-tools_0.4.8-14ubuntu5~lp644489_amd64.deb) ...
[...]
Preparing to replace multipath-tools-boot 0.4.8-14ubuntu4 (using .../multipath-tools-boot_0.4.8-14ubuntu5~lp644489_all.deb) ...
[...]
[jwm at pxe-237.roch.ny:pts/0 ~> for i in /dev/sd[abcd]; do sudo mpath_prio_netapp $i; done
4
1
4
1
[jwm at pxe-237.roch.ny:pts/0 ~> psg multi
root     30498 30498  0.0  0.0  85396  3500 ?     SLl  futex_ 13:24 /sbin/multipathd
root     30498 30500  0.0  0.0  85396  3500 ?     SLl  futex_ 13:24 /sbin/multipathd
root     30498 30514  0.0  0.0  85396  3500 ?     SLl  dm_wai 13:24 /sbin/multipathd
root     30498 30515  0.0  0.0  85396  3500 ?     SLl  hrtime 13:24 /sbin/multipathd
root     30498 30516  0.0  0.0  85396  3500 ?     SLl  skb_re 13:24 /sbin/multipathd
root     30498 30517  0.0  0.0  85396  3500 ?     SLl  poll_s 13:24 /sbin/multipathd
root     30498 30518  0.0  0.0  85396  3500 ?     SLl  futex_ 13:24 /sbin/multipathd
[jwm at pxe-237.roch.ny:pts/0 ~> sudo udevadm monitor
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent

[no events generated]

john
-- 
John Morrissey          _o            /\         ----  __o
jwm at horde.net        _-< \_          /  \       ----  <  \,
www.horde.net/    __(_)/_(_)________/    \_______(_) /_(_)__

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https://bugs.launchpad.net/bugs/644489

Title:
  constantly changes /dev/disk/by-id/{scsi,wwn}-* LUN symlinks with
  multipathing

Status in “multipath-tools” package in Ubuntu:
  Confirmed
Status in “udev” package in Ubuntu:
  New

Bug description:
  Binary package hint: udev

  udevd constantly changes LUN device node symlinks (devices/LUNs, not
  the partition nodes) in /dev/disk/by-id. udevd uses ~15% of CPU and
  system time is using ~50-60%.

  For example:

  [jwm at syslog01.roch.ny:pts/0 /dev/disk/by-id> ls -l wwn-0x60a98000486e5339576f596675735354 wwn-0x60a98000486e5339576f596675744c36 scsi-360a98000486e5339576f596675735354 scsi-360a98000486e5339576f596675744c36; sleep 1; echo '======'; ls -l wwn-0x60a98000486e5339576f596675735354 wwn-0x60a98000486e5339576f596675744c36 scsi-360a98000486e5339576f596675735354 scsi-360a98000486e5339576f596675744c36
  lrwxrwxrwx 1 root root 9 2010-09-21 16:12 scsi-360a98000486e5339576f596675735354 -> ../../sde
  lrwxrwxrwx 1 root root 9 2010-09-21 16:12 scsi-360a98000486e5339576f596675744c36 -> ../../sdf
  lrwxrwxrwx 1 root root 9 2010-09-21 16:12 wwn-0x60a98000486e5339576f596675735354 -> ../../sde
  lrwxrwxrwx 1 root root 9 2010-09-21 16:12 wwn-0x60a98000486e5339576f596675744c36 -> ../../sdf
  ======
  lrwxrwxrwx 1 root root 9 2010-09-21 16:12 scsi-360a98000486e5339576f596675735354 -> ../../sdg
  lrwxrwxrwx 1 root root 9 2010-09-21 16:12 scsi-360a98000486e5339576f596675744c36 -> ../../sdh
  lrwxrwxrwx 1 root root 9 2010-09-21 16:12 wwn-0x60a98000486e5339576f596675735354 -> ../../sdg
  lrwxrwxrwx 1 root root 9 2010-09-21 16:12 wwn-0x60a98000486e5339576f596675744c36 -> ../../sdh

  All other device nodes stay the same, such as the device nodes for the
  partitions:

  [jwm at syslog01.roch.ny:pts/0 /dev/disk/by-id> ls -l scsi-360a98000486e5339576f596675735354-part1; sleep 1; echo '======'; ls -l scsi-360a98000486e5339576f596675735354-part1
  lrwxrwxrwx 1 root root 10 2010-09-21 15:47 scsi-360a98000486e5339576f596675735354-part1 -> ../../sdg1
  ======
  lrwxrwxrwx 1 root root 10 2010-09-21 15:47 scsi-360a98000486e5339576f596675735354-part1 -> ../../sdg1

  
  I'm not entirely sure whether this is udev's problem or something related to multipathing. Our most recent experience with multipathing is the last LTS release (hardy), which doesn't exhibit this behavior given similar configurations.

  
  [jwm at syslog01.roch.ny:pts/0 ~> sudo multipath -ll
  rootvol (360a98000486e5339576f596675735354) dm-1 NETAPP  ,LUN           
  [size=36G][features=1 queue_if_no_path][hwhandler=0]
  \_ round-robin 0 [prio=8][active]
   \_ 2:0:2:0 sda 8:0   [active][ready]
   \_ 3:0:2:0 sde 8:64  [active][ready]
  \_ round-robin 0 [prio=2][enabled]
   \_ 3:0:3:0 sdg 8:96  [active][ready]
   \_ 2:0:3:0 sdc 8:32  [active][ready]
  syslog-data (360a98000486e5339576f596675744c36) dm-0 NETAPP  ,LUN           
  [size=1.0T][features=1 queue_if_no_path][hwhandler=0]
  \_ round-robin 0 [prio=8][active]
   \_ 2:0:2:1 sdb 8:16  [active][ready]
   \_ 3:0:2:1 sdf 8:80  [active][ready]
  \_ round-robin 0 [prio=2][enabled]
   \_ 3:0:3:1 sdh 8:112 [active][ready]
   \_ 2:0:3:1 sdd 8:48  [active][ready]
  [jwm at syslog01.roch.ny:pts/0 ~> cat /etc/multipath.conf 
  multipaths {
          multipath {
                  wwid            360a98000486e5339576f596675735354
                  alias           rootvol
          }
          multipath {
                  wwid            360a98000486e5339576f596675744c36
                  alias           syslog-data
          }
  }

  devices {
          device {
                  vendor                  "NETAPP  "
                  product                 "LUN "
                  path_checker            tur
                  path_grouping_policy    group_by_prio
                  prio_callout            "/sbin/mpath_prio_netapp /dev/%n"
                  failback                immediate
                  rr_min_io               128
                  no_path_retry           queue
          }
  }

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