Document fins/I0629-1
FIN #: I0629-1
SYNOPSIS: T3 Array display with using DM with VxVM
DATE: Dec/14/00
KEYWORDS: T3 Array display with using DM with VxVM
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- Sun Proprietary/Confidential: Internal Use Only -
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FIELD INFORMATION NOTICE
(For Authorized Distribution by SunService)
SYNOPSIS: How to correctly display disk pathnames for T3 arrays
when using Dynamic Multipathing with Veritas Volume Manager.
TOP FIN/FCO REPORT: No
PRODUCT_REFERENCE: Veritas Volume Manager: 3.0.2, 3.0.3, 3.0.4, 3.1
PRODUCT CATEGORY: Storage / T3
PRODUCTS AFFECTED:
Mkt_ID Platform Model Description Serial Number
------ -------- ----- ----------- -------------
Systems Affected
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- ANYSYS - System Platform Independent -
X-Options Affected
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- T3 ALL T3 StorEdge Array -
PART NUMBERS AFFECTED:
Part Number Description Model
----------- ----------- -----
- - -
REFERENCES:
BugId: 4355813 - Partner Group multipathing not working as expected with
vxvm & dmp
PROBLEM 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
<diskname>'
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 <diskname>'
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)
---
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| x | REACTIVE (As Required)
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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 <diskname>
For example,
#vxdisk list c1t2d0s2
This will display the disk multipathing information.
COMMENTS:
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Implementation Footnote:
i) In case of MANDATORY FINs, Enterprise Services will attempt to
contact all affected customers to recommend implementation of
the FIN.
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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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