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storageaixsan

Multiple Paths in powermt display command in AIX

I have a hard time in getting this. I am not getting how there are eight paths from the server to storage. Can anyone help me with a diagram of the connections from server-switch-storage.

1) Are these four HBA ports? I guess so.

[Dev][root@fdcc ~]# lsdev -Cc adapter |grep fcs*

fcs0   Available 11-T1 Virtual Fibre Channel Client Adapter

fcs1   Available 12-T1 Virtual Fibre Channel Client Adapter

fcs2   Available 13-T1 Virtual Fibre Channel Client Adapter

fcs3   Available 14-T1 Virtual Fibre Channel Client Adapter

2) No idea about below? Please explain about this.

[Dev][root@fdcc ~]# lspath

Enabled hdisk1 vscsi0

Enabled hdisk0 vscsi0

Enabled hdisk2 vscsi0

Enabled hdisk1 vscsi1

Enabled hdisk0 vscsi1

Enabled hdisk2 vscsi1

3) These are HBA ports. Right?

[Dev][root@fdcc ~]#  powermt display hba_mode

Hitachi logical device count=74

==============================================================================

----- Host Bus Adapters ---------  ------ I/O Paths -----  Stats

###  HW Path                       Summary   Total   Dead  Q-IOs Mode

==============================================================================

   0 fscsi0                        optimal     148      0       0  Enabled

   1 fscsi1                        optimal     148      0       0  Enabled

   2 fscsi2                        optimal     148      0       0  Enabled

   3 fscsi3                        optimal     148      0       0  Enabled

4) These are paths and I don't understand how fscsi0 goes to 3A and 3C. How can the port have two connections to two controllers. I have hard time in getting this.

[Dev][root@fdcc ~]# powermt display paths

Hitachi logical device count=74

==============================================================================

----- Host Bus Adapters --------- ------ Storage System -----    - I/O Paths -

###  HW Path                         ID           Interface     Total    Dead

==============================================================================

   0 fscsi0                       471399           3C               74       0

   0 fscsi0                       471399           3A               74       0

   1 fscsi1                       471399           4C               74       0

   1 fscsi1                       471399           4A               74       0

   2 fscsi2                       471399           3C               74       0

   2 fscsi2                       471399           3A               74       0

   3 fscsi3                       471399           4C               74       0

   3 fscsi3                       471399           4A               74       0

5) What is the Wt-Q column?

[Dev][root@fdcc ~]# powermt display port_mode



Storage class = Hitachi

==============================================================================

----------- Storage System ---------------     -- I/O Paths --   --- Stats ---

    ID              Interface         Wt_Q      Total    Dead    Q-IOs  Mode

==============================================================================

    471399           4C                256        148       0        0  Enabled

    471399           4A                256        148       0        0  Enabled

    471399           3C                256        148       0        0  Enabled

    471399           3A                256        148       0        0  Enabled
Solution

  • There are 8 paths to the LDEV, because you are dealing with Fibre-channel SAN, where FC traffic between HBA ports and Storage ports is routed through Fibre-channel switched fabrics. Best practices urge to use so-called Dual-Fabric configurations, therefore based on your outputs, I can suppose, HBAs fscsi0, fscsi2 along with ports 3A, 3C are connected to the first fabric, while fscsi1/fscsi3 and 4A/4C are in the second fabric.

    Wt-Q looks for me like "Wait queue". For modern enterprise Hitachi storage arrays the recommended maximum number of SCSI commands is 2048 per FC-port, 32 per logical unit but you must consult the manual four your model.

    enter image description here

    A new picture, that represents physical possible Fabrics connection is attached: enter image description here

    Logical connections are depicted in the first pictue. The mechanism which rules connections on logical level is called "Zoning", and saying simple it can be somehow compared to VLANs in LAN switches. So you can specify which WWNs and/or ports are allowed to communicate.