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- Sun Proprietary/Confidential: Internal Use Only -
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                            FIELD INFORMATION NOTICE
                  (For Authorized Distribution by SunService)

FIN #: I0629-1

Create Date: Dec/14/00

Keywords: 

T3 Array display with using DM with VxVM

Top FIN/FCO Report: No

Products Reference: Veritas Volume Manager: 3.0.2, 3.0.3, 3.0.4, 3.1

Product Category: Storage / T3

Product Affected: 

Mkt_ID   Platform   Model   Description             Serial Number
------   --------   -----   -----------             -------------
Systems Affected
----------------
  -       ANYSYS      -     System Platform Independent    -

X-Options Affected
------------------
  -       T3         ALL    T3 StorEdge Array              -

Parts Affected: 

Part Number   Description   Model
-----------   -----------   -----
     -             -          -

References: 

BugId: 4355813 - Partner Group multipathing not working as expected with 
                 vxvm & dmp

Issue Description: 

When StorEdge T3 Arrays are installed in a partner pair configuration,
there has been some confusion about how to properly display multipathing 
information for a particular disk.  Customers may use the 'vxdisk list' 
command from Veritas Volume Manager and the output will show all disks 
for both T3's as using the same controller.  This may appear to be a 
configuration problem and a cause of concern for the customer.
 
The T3 array in partner pair configuration provides 2 paths to each LUN.  
One path is considered the primary and the other path is considered the
secondary for any given LUN.  In normal operation, all I/O for a particular
LUN goes down the primary path.  If the primary path for a LUN fails, I/O
for that LUN is sent down the secondary path.  In order to balance the I/O
load, half of the LUN's use one path as the primary and half use the other.  
This means that both paths are considered primary for some LUN's and
secondary for some LUN's.  Because there is a primary and secondary path
for each LUN, the T3 is an Active/Passive type array.

When the Dynamic Multipathing (DMP) driver in Veritas Volume Manager (VxVM)
scans the device list looking for devices that are accessed through more than 
one controller, it assigns the name of the disk media record based on which 
controller is probed first.  Because of this, all the LUN's in the array will 
have DMP records that start with the same controller.  The DMP record name does 
not indicate which controller is in use as the primary path for a particular LUN.
The multipathing information can be displayed by the 'vxdisk list ' 
command.

EXAMPLE: 
The array is attached to the host through 2 controllers, C1 and
C4.  One LUN uses the C1 path as the primary and C4 as the secondary.  
The other LUN uses C4 as the primary and C1 as the secondary.  Both LUN's
have DMP records that begin with C1.

# vxdisk list
DEVICE       TYPE      DISK         GROUP        STATUS

c1t2d0s2     sliced    disk01       rootdg       online
c1t2d1s2     sliced    disk02       rootdg       online


DMP does know which path is primary and which is secondary for each LUN.
That information can be displayed with the 'vxdisk list ' command.

# vxdisk list c1t2d0s2
Device:    c1t2d0s2
devicetag: c1t2d0
type:      sliced
hostid:    tpsw-154
disk:      name=disk01 id=966899066.1066.tpsw-154
group:     name=rootdg id=966899051.1025.tpsw-154
flags:     online ready autoconfig autoimport imported
pubpaths:  block=/dev/vx/dmp/c1t2d0s4 char=/dev/vx/rdmp/c1t2d0s4
privpaths: block=/dev/vx/dmp/c1t2d0s3 char=/dev/vx/rdmp/c1t2d0s3
version:   2.1
iosize:    min=512 (bytes) max=2048 (blocks)
public:    slice=4 offset=0 len=279707648
private:   slice=3 offset=1 len=8191
update:    time=966899613 seqno=0.9
headers:   0 248
configs:   count=1 len=6027
logs:      count=1 len=913
Defined regions:
config   priv 000017-000247[000231]: copy=01 offset=000000 enabled
config   priv 000249-006044[005796]: copy=01 offset=000231 enabled
log        priv 006045-006957[000913]: copy=01 offset=000000 enabled
Multipathing information:
numpaths:   2
c1t2d0s2        state=enabled   type=secondary
c4t1d0s2        state=enabled   type=primary
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

# vxdisk list c1t2d1s2
Device:    c1t2d1s2
devicetag: c1t2d1
type:      sliced
hostid:    tpsw-154
disk:      name=disk02 id=966899118.1145.tpsw-154
group:     name=rootdg id=966899051.1025.tpsw-154
flags:     online ready autoconfig autoimport imported
pubpaths:  block=/dev/vx/dmp/c1t2d1s4 char=/dev/vx/rdmp/c1t2d1s4
privpaths: block=/dev/vx/dmp/c1t2d1s3 char=/dev/vx/rdmp/c1t2d1s3
version:   2.1
iosize:    min=512 (bytes) max=2048 (blocks)
public:    slice=4 offset=0 len=279707648
private:   slice=3 offset=1 len=8191
update:    time=966899613 seqno=0.7
headers:   0 248
configs:   count=1 len=6027
logs:      count=1 len=913
Defined regions:
config   priv 000017-000247[000231]: copy=01 offset=000000 enabled
config   priv 000249-006044[005796]: copy=01 offset=000231 enabled
log        priv 006045-006957[000913]: copy=01 offset=000000 enabled
Multipathing information:
numpaths:   2
c1t2d1s2        state=enabled   type=primary
c4t1d1s2        state=enabled   type=secondary
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The multipathing information shows that C1 is primary for disk02 and
secondary for disk01, while C4 is primary for disk01 and secondary for
disk02.  If the primary path fails, DMP will switch to the secondary path
and the type will show as "disabled" for the failed path.

Implementation: 

---
        |   |   MANDATORY (Fully Pro-Active)
         ---    
         
  
         ---
        |   |   CONTROLLED PRO-ACTIVE (per Sun Geo Plan) 
         --- 
         
                                
         ---
        | x |   REACTIVE (As Required)
         ---

Corrective Action: 

The following recommendation is provided as a guideline for authorized
Enterprise Services Field Representatives who may be encountering the 
above mentioned problem.

In order to display the true device pathnames for T3 arrays using
DMP (Dynamic Multipathing) with VxVM, run the following command:

   #vxdisk list 

   For example,

   #vxdisk list c1t2d0s2
	
This will display the disk multipathing information.

Comments: 

------------------------------------------------------------------------------

Implementation Footnote: 

i)   In case of MANDATORY FINs, Enterprise Services will attempt to    
     contact all affected customers to recommend implementation of 
     the FIN. 
   
ii)  For CONTROLLED PROACTIVE FINs, Enterprise Services mission critical    
     support teams will recommend implementation of the FIN  (to their  
     respective accounts), at the convenience of the customer. 

iii) For REACTIVE FINs, Enterprise Services will implement the FIN as the   
     need arises.
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