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[weiweigu <gu.weiwei@xxxxxxxxxx>]

Public bug reported:

tested environment:
iscsi_use_multipath=True and iscsI volume backed is ZTE KS3200.
The nova compute note connects to KS3200 with four ports. And launch an instance which boots form a volume. 

I see there are four sd* devices belong to the multipath device "/dev/mapper/mpathc".
[root@opencos170 ~]# multipath -ll
mpathc (3600000e00d280000002800e2000c0000) dm-3 FUJITSU ,ETERNUS_DXL     
size=1.0T features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=50 status=active
| |- 25:0:0:1 sdf 8:80  active ready  running
| `- 24:0:0:1 sdi 8:128 active ready  running
`-+- policy='round-robin 0' prio=10 status=enabled
  |- 22:0:0:1 sdh 8:112 active ready  running
  `- 23:0:0:1 sde 8:64  active ready  running

I disconnect one port of KS3200. And attach a volume to the instance.
Then I see the sdi device lost.  There are only three sd* devices.
[root@opencos170 ~]# multipath -ll
mpathc (3600000e00d280000002800e2000c0000) dm-3 FUJITSU ,ETERNUS_DXL     
size=1.0T features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=50 status=active
| |- 25:0:0:1 sdf 8:80  active ready  running
`-+- policy='round-robin 0' prio=10 status=enabled
  |- 22:0:0:1 sdh 8:112 active ready  running
  `- 23:0:0:1 sde 8:64  active ready  running

I connect the KS3200 port,but the sdi device never appear.

After a lot of repetition of failure,I found the reason is the command "multipath -r".
If the link between the compute note and the zte KS3200 is broken, the sd* device lost after execute the command "multipath -r".
If the link is ok, the sd* device appear after execute the command "multipath -r".

Is the command "multipath -r" necessary when attaching or detaching
volume. Whether can be removed?

** Affects: nova
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1414865

Title:
  Lost the sd* devices which belong to the multipath device.

Status in OpenStack Compute (Nova):
  New

Bug description:
  tested environment:
  iscsi_use_multipath=True and iscsI volume backed is ZTE KS3200.
  The nova compute note connects to KS3200 with four ports. And launch an instance which boots form a volume. 

  I see there are four sd* devices belong to the multipath device "/dev/mapper/mpathc".
  [root@opencos170 ~]# multipath -ll
  mpathc (3600000e00d280000002800e2000c0000) dm-3 FUJITSU ,ETERNUS_DXL     
  size=1.0T features='0' hwhandler='0' wp=rw
  |-+- policy='round-robin 0' prio=50 status=active
  | |- 25:0:0:1 sdf 8:80  active ready  running
  | `- 24:0:0:1 sdi 8:128 active ready  running
  `-+- policy='round-robin 0' prio=10 status=enabled
    |- 22:0:0:1 sdh 8:112 active ready  running
    `- 23:0:0:1 sde 8:64  active ready  running

  I disconnect one port of KS3200. And attach a volume to the instance.
  Then I see the sdi device lost.  There are only three sd* devices.
  [root@opencos170 ~]# multipath -ll
  mpathc (3600000e00d280000002800e2000c0000) dm-3 FUJITSU ,ETERNUS_DXL     
  size=1.0T features='0' hwhandler='0' wp=rw
  |-+- policy='round-robin 0' prio=50 status=active
  | |- 25:0:0:1 sdf 8:80  active ready  running
  `-+- policy='round-robin 0' prio=10 status=enabled
    |- 22:0:0:1 sdh 8:112 active ready  running
    `- 23:0:0:1 sde 8:64  active ready  running

  I connect the KS3200 port,but the sdi device never appear.

  After a lot of repetition of failure,I found the reason is the command "multipath -r".
  If the link between the compute note and the zte KS3200 is broken, the sd* device lost after execute the command "multipath -r".
  If the link is ok, the sd* device appear after execute the command "multipath -r".

  Is the command "multipath -r" necessary when attaching or detaching
  volume. Whether can be removed?

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