Serviceguard Extended Distance Cluster (EDC) with VxVM/CVM Mirroring on HP-UX, May 2008

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Figure 6 shows the objects of a mirrored data volume, including its attached DCO volume:

Figure 6. Mirrored VxVM volume with attached DCO volume

vol01

volume|

plex

associated

DCO volume

plex

subdisk

VM disk

physical

disk / LUN

vol01_dcl

vol01_dcl-01

DC1-disk02-01

DC1-disk02

DC1-disk02-01

vol01_dcl-02

DC2-disk02-01

DC2-disk02

DC2-disk02-01

vol01_dcl-02

UID

ESC ENTER

UID

ESC ENTER

StorageWorks

hsv210

StorageWorks

hsv210

hp St or ageW or ks

Bay 14Bay 1

300GB 15k

UID

ESC ENTER

UID

ESC ENTER

StorageWorks

hsv210

StorageWorks

hsv210

hp St or ageW or ks

Bay 14Bay 1

300GB 15k

UID

ESC ENTER

UID

ESC ENTER

StorageWorks

hsv210

StorageWorks

hsv210

hp StorageWorks

Bay 14Bay 1

300GB 15k

UID

ESC ENTER

UID

ESC ENTER

StorageWorks

hsv210

StorageWorks

hsv210

hp StorageWorks

Bay 14Bay 1

300GB 15k

DC2-disk02-01

DC2-disk02

DC1-disk02-01

DC1-disk02

DC1-disk01

vol01-01

DC1-disk01-01

vol01-01

DC1-disk01

DC2-disk01

vol01-02

DC2-disk01-01

vol01-02

DC2-disk01-01

DC2-disk01

When VxVM creates the attached DCO volume it simply adds “dcl” (an acronym for “data change

log”) to the names of the data volume objects. For example,

• volume: vol01 Æ vol01_dcl

• plex: vol01-01 Æ vol01_dcl-01

• plex: vol01-02 Æ vol01_dcl-02

The following DCO related options should be specified with the vxassist command when a shared

volume for an EDC is created:

• logtype=dco

Persistent FastResync requires a data change object (DCO) volume to be associated with each EDC

volume. The DCO volume holds the map that tracks changes to the EDC volume while a plex is

detached or broken off from it.

• dcoversion=20

With version 20 DCO, part of the volume can be used to store the DRL maps.