[dm-devel] why doesn't multipathd use the device?

[Christophe Varoqui]

On jeu., 2012-06-21 at 16:54 -0700, Brian Bunker wrote:
> Hello everyone,
> 
> 
> We have hit this problem a couple of times now on our RHEL 6.2
> initiators using our FC target. We have many dm devices which should
> have 4 paths to each. Sometimes we see that some of the dm devices do
> not have the 4 paths. The underlying /dev/sd devices do exist but they
> are not used by the dm device. Here is what I see:
> 
> 
> mpathbbt (3624a9370f9b69331bb3d16650001000b) dm-11 PURE,FlashArray
> size=500G features='0' hwhandler='0' wp=rw
> `-+- policy='round-robin 0' prio=1 status=active
>  |- 1:0:1:12 sds  65:32  active ready running
>  `- 1:0:0:12 sdae 65:224 active ready running
> 
> 
> However there are devices for the remaining two paths they are just
> not being used by multipathd:
> 
> 
> /dev/sg18  1 0 1 12  0  /dev/sds  PURE      FlashArray        100 
> /dev/sg30  1 0 0 12  0  /dev/sdae  PURE      FlashArray        100 
> /dev/sg39  0 0 1 12  0  /dev/sdan  PURE      FlashArray        100 
> /dev/sg48  0 0 0 12  0  /dev/sdaw  PURE      FlashArray        100
> 
> 
> You can see by the LUN serial number that the devices do point to the
> same LUN on the array. I am including just the LUN serial number, page
> 0x80, in the interest of space page 0x83's NAA number also matches for
> the 4 devices:
> 
> 
> root at r13init31 ~]# sg_inq -p 0x80 /dev/sg18
> VPD INQUIRY: Unit serial number page
> Unit serial number: F9B69331BB3D16650001000B
> 
> 
> [root at r13init31 ~]# sg_inq -p 0x80 /dev/sg30
> VPD INQUIRY: Unit serial number page
> Unit serial number: F9B69331BB3D16650001000B
> 
> 
> [root at r13init31 ~]# sg_inq -p 0x80 /dev/sg39
> VPD INQUIRY: Unit serial number page
> Unit serial number: F9B69331BB3D16650001000B
> 
> 
> [root at r13init31 ~]# sg_inq -p 0x80 /dev/sg48
> VPD INQUIRY: Unit serial number page
> Unit serial number: F9B69331BB3D16650001000B

> 
> Any ideas why the paths are being rejected by domap?
> 
Have you tried the "group_by_serial" path grouping policy ?
There might be funny side effects if the wwid discovered on paths is not
the same though ...

Can you post the multipath -v3 output concerning those 4 paths
discovery.

Regard,
cvaroqui