Multipath - dual path - fc | Unix Knowledge base

Step 1: Use the “ioscan” command to get some fiber card info

# ioscan -fnC fc
 Class     I  H/W Path  Driver S/W State   H/W Type     Description
 ================================================================
 fc        2  0/3/1/0   fcd   CLAIMED     INTERFACE    HP AB379-60101 4Gb Dual Port PCI/PCI-X Fibre Channel Adapter (FC Port 1)
/dev/fcd2
 fc        3  0/3/1/1   fcd   CLAIMED     INTERFACE    HP AB379-60101 4Gb Dual Port PCI/PCI-X Fibre Channel Adapter (FC Port 2)
/dev/fcd3
#

This gives us the two HBA devices and their hardware paths:
/dev/fcd2: 0/3/1/0
/dev/fcd3: 0/3/1/1

Step 2: Use the “fcmsutil” command to get some WWN info

# fcmsutil /dev/fcd2

                           Vendor ID is = 0x1077
                           Device ID is = 0x2422
            PCI Sub-system Vendor ID is = 0x103C
                   PCI Sub-system ID is = 0x12D7
                               PCI Mode = PCI-X 133 MHz
                       ISP Code version = 4.4.4
                       ISP Chip version = 3
                               Topology = PTTOPT_FABRIC
                             Link Speed = 4Gb
                     Local N_Port_id is = 0x010500
                  Previous N_Port_id is = None
            N_Port Node World Wide Name = 0x50060b000069b1d9
N_Port Port World Wide Name = 0x50060b000069b1d8
            Switch Port World Wide Name = 0x200500051e05b304
            Switch Node World Wide Name = 0x100000051e05b304
              N_Port Symbolic Port Name = odevux34_fcd2
              N_Port Symbolic Node Name = odevux34_HP-UX_B.11.31
Driver state = ONLINE
Hardware Path is = 0/3/1/0
                     Maximum Frame Size = 2048
         Driver-Firmware Dump Available = NO
         Driver-Firmware Dump Timestamp = N/A
                         Driver Version = @(#) fcd B.11.31.0909 Jun  8 2009

# fcmsutil /dev/fcd3

                           Vendor ID is = 0x1077
                           Device ID is = 0x2422
            PCI Sub-system Vendor ID is = 0x103C
                   PCI Sub-system ID is = 0x12D7
                               PCI Mode = PCI-X 133 MHz
                       ISP Code version = 4.4.4
                       ISP Chip version = 3
                               Topology = PTTOPT_FABRIC
                             Link Speed = 4Gb
                     Local N_Port_id is = 0x010500
                  Previous N_Port_id is = None
            N_Port Node World Wide Name = 0x50060b000069b1db
N_Port Port World Wide Name = 0x50060b000069b1da
            Switch Port World Wide Name = 0x200500051e05940a
            Switch Node World Wide Name = 0x100000051e05940a
              N_Port Symbolic Port Name = odevux34_fcd3
              N_Port Symbolic Node Name = odevux34_HP-UX_B.11.31
Driver state = ONLINE
Hardware Path is = 0/3/1/1
                     Maximum Frame Size = 2048
         Driver-Firmware Dump Available = NO
         Driver-Firmware Dump Timestamp = N/A
                         Driver Version = @(#) fcd B.11.31.0909 Jun  8 2009

#
We can see the WWN’s that will appear on the switches (and also in the host group on the storage manager) as well as the status (“ONLINE”) and the hardware path.

Step 3: Use “ioscan” to find the external storage disks in question

# ioscan -f -n -C disk
 Class     I  H/W Path       Driver S/W State   H/W Type     Description
 =======================================================================
 disk      2  0/0/2/0.0.0.0  sdisk   CLAIMED     DEVICE       TEAC    DV-28E-C
                           /dev/dsk/c0t0d0   /dev/rdsk/c0t0d0
 disk      0  0/1/1/0.0.0    sdisk   CLAIMED     DEVICE       HP 73.4GST373455LC
                           /dev/dsk/c2t0d0   /dev/rdsk/c2t0d0
 disk      1  0/1/1/1.2.0    sdisk   CLAIMED     DEVICE       HP 73.4GST373455LC
                           /dev/dsk/c3t2d0   /dev/rdsk/c3t2d0
disk      6  0/3/1/0.1.7.0.0.0.0  sdisk   CLAIMED     DEVICE       IBM     1722-600
                           /dev/dsk/c9t0d0   /dev/rdsk/c9t0d0
 disk     47  0/3/1/0.1.7.0.0.3.7  sdisk   CLAIMED     DEVICE       IBM     Universal Xport
                           /dev/dsk/c9t3d7   /dev/rdsk/c9t3d7
disk     30  0/3/1/1.1.7.0.0.0.0  sdisk   CLAIMED     DEVICE       IBM     1722-600
                           /dev/dsk/c8t0d0   /dev/rdsk/c8t0d0
 disk     48  0/3/1/1.1.7.0.0.3.7  sdisk   CLAIMED     DEVICE       IBM     Universal Xport
                           /dev/dsk/c8t3d7   /dev/rdsk/c8t3d7
#

Above you can see there are two IBM paths. This represents two single direct paths to the same storage.
/dev/dsk/c9t0d0 with hardware path 0/3/1/0.1.7.0.0.0.0
/dev/dsk/c8t0d0 with hardware path 0/3/1/1.1.7.0.0.0.0
And if you remember from the above “ioscan -fNc fc” output
/dev/fcd2 (device driver) = 0/3/1/0 (physical hardware path)
/dev/fcd3 (device driver) = 0/3/1/1 (physical hardware path)
Which means:
/dev/dsk/c9t0d0 is talking on the fiber port designated as /dev/fcd2
/dev/dsk/c8t0d0 is talking on the fiber port designated as /dev/fcd3
This gives us some good possible debugging info, especially if we later have access to the switch and can see error logs on the switch, since on the switch and in the external storage manager GUI:
/dev/fcd2 will have the port name 0x50060b000069b1d8
/dev/fcd3 will have the port name 0x50060b000069b1da
Next command:

# ioscan -f -n -N -C disk
 Class     I  H/W Path  Driver S/W State   H/W Type     Description
 ===================================================================
 disk      3  64000/0xfa00/0x0   esdisk   CLAIMED     DEVICE       HP 73.4GST373455LC
                      /dev/disk/disk3   /dev/rdisk/disk3
 disk      4  64000/0xfa00/0x1   esdisk   CLAIMED     DEVICE       HP 73.4GST373455LC
                      /dev/disk/disk4   /dev/rdisk/disk4
 disk      5  64000/0xfa00/0x2   esdisk   CLAIMED     DEVICE       TEAC    DV-28E-C
                      /dev/disk/disk5   /dev/rdisk/disk5
disk     46  64000/0xfa00/0xe   esdisk   CLAIMED     DEVICE       IBM     1722-600
                      /dev/disk/disk46   /dev/rdisk/disk46
 disk     50  64000/0xfa00/0xf   esdisk   CLAIMED     DEVICE       IBM     Universal Xport
                      /dev/disk/disk50   /dev/rdisk/disk50
 disk     51  64000/0xfa00/0x10  esdisk   CLAIMED     DEVICE       IBM     Universal Xport
                      /dev/disk/disk51   /dev/rdisk/disk51
#

Here you can see /dev/disk/disk46 is the multipath disk with hardware path 64000/0xfa00/0xe.
Meaning when you refer to the disk through the device /dev/disk/disk46, that device will write to the disk using one of the two direct paths of /dev/dsk/c9t0d0 and /dev/dsk/c8t0d0 depending on the settings for load balancing, preferred path, etc.
So far: mostly what we have done is determined that yes there is a multipath, and yes it seems to be working.

Step 4: Use the “scsimgr” command to get load balancing

So let’s check out that multipath
Using the hardware path for the multipath disk, let’s see what the load balancing policy is.
# scsimgr get_attr -H 64000/0xfa00/0xe -a load_bal_policy

        SCSI ATTRIBUTES FOR LUN : 64000/0xfa00/0xe

name = load_bal_policy
current = round_robin
default = round_robin
 saved =

#

AY! THERE’S THE RUB!

And there we are. The HP system is using a round-robin load balancing policy so it will keep switching the path used, which is why our storage manager is going crazy.

Step 5: Use the “scsimgr” command to set the load balancing to “preferred path”

# scsimgr save_attr -H 64000/0xfa00/0xe -a load_bal_policy="preferred_path"
And let’s make sure it took:
# scsimgr get_attr -H 64000/0xfa00/0xe -a load_bal_policy

        SCSI ATTRIBUTES FOR LUN : 64000/0xfa00/0xe

name = load_bal_policy
current = preferred_path
 default = round_robin
saved = preferred_path

#

Step 6: Telling HP-UX Which Path To Use As The Preferred Path

And now we have to tell the HP-UX system WHICH path to use as the preferred path.
Unfortunately, this will be a 50/50 guess. Because I do not have access to the switch. I can see on the Storage Manager GUI it wants the preferred path to be on Controller B. However, on the storage manager GUI you only define host groups which means you throw in Storage Controller A and Storage Controller B into the same host group as the two fiber ports on the HP-UX server.
If I had access to the switch, I might have an easier time seeing which one of the two HP-UX fiber ports is talking to Controller B.
Since I can’t see that, the only thing to do is set the path to one, see if the Storage Manager complains, and if there are no complaints, we guessed right! If it complains, than we set it to the other path.
First, we can verify that no preferred path is set:
# scsimgr get_attr -D /dev/rdisk/disk46 -a preferred_path

        SCSI ATTRIBUTES FOR LUN : /dev/rdisk/disk46

name = preferred_path
current =
 default =
 saved =

#
And let’s take a quick look at the hardware paths again
# scsimgr lun_map -D /dev/rdisk/disk46

        LUN PATH INFORMATION FOR LUN : /dev/rdisk/disk46

Total number of LUN paths     = 2
 World Wide Identifier(WWID)    = 0x600a0b8000225d7d00005b3150fd79bf

LUN path : lunpath36
 Class                         = lunpath
 Instance                      = 36
Hardware path                 = 0/3/1/0.0x200700a0b81984d6.0x4000000000000000
 SCSI transport protocol       = fibre_channel
 State                         = ACTIVE
 Last Open or Close state      = ACTIVE

LUN path : lunpath35
 Class                         = lunpath
 Instance                      = 35
Hardware path                 = 0/3/1/1.0x200600a0b81984d5.0x4000000000000000
 SCSI transport protocol       = fibre_channel
 State                         = ACTIVE
 Last Open or Close state      = ACTIVE

#
And now we pick one. And set it

# scsimgr save_attr -D /dev/rdisk/disk46 -a preferred_path=0/3/1/0.0x200700a0b81984d6.0x4000000000000000
 Value of attribute preferred_path saved successfully
#

And now check it
# scsimgr get_attr -D /dev/rdisk/disk46 -a preferred_path

        SCSI ATTRIBUTES FOR LUN : /dev/rdisk/disk46

name = preferred_path
current = 0/3/1/0.0x200700a0b81984d6.0x4000000000000000(lunpath36)
 default =
saved = 0/3/1/0.0x200700a0b81984d6.0x4000000000000000(lunpath36)

#
If it complains, then try the other hardware path. If it doesn’t, then you’re good

Unix Knowledge base

Multipath - dual path - fc

Step 1: Use the “ioscan” command to get some fiber card info

Step 2: Use the “fcmsutil” command to get some WWN info

Step 3: Use “ioscan” to find the external storage disks in question

Step 4: Use the “scsimgr” command to get load balancing

AY! THERE’S THE RUB!

Step 5: Use the “scsimgr” command to set the load balancing to “preferred path”

Step 6: Telling HP-UX Which Path To Use As The Preferred Path

sangeethakumar

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Multipath - dual path - fc

Step 1: Use the “ioscan” command to get some fiber card info

Step 2: Use the “fcmsutil” command to get some WWN info

Step 3: Use “ioscan” to find the external storage disks in question

Step 4: Use the “scsimgr” command to get load balancing

AY! THERE’S THE RUB!

Step 5: Use the “scsimgr” command to set the load balancing to “preferred path”

Step 6: Telling HP-UX Which Path To Use As The Preferred Path

sangeethakumar

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