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Administering volumes

Preparing a volume for DRL and instant snapshots

Note: The vxsnap prepare command automatically enables Persistent FastResync on the volume. Persistent FastResync is also set automatically on any snapshots that are generated from a volume on which this feature is enabled.

If the volume is a RAID-5 volume, it is converted to a layered volume that can be used with instant snapshots and Persistent FastResync. See “Using a DCO and DCO volume with a RAID-5 volume” on page 277 for details.

By default, a version 20 DCO volume contains 32 per-volume maps. If you require more maps than this, you can use the vxsnap addmap command to add more maps. See the vxsnap(1M) manual page for details of this command.

Specifying storage for version 20 DCO plexes

If the disks that contain volumes and their snapshots are to be moved into different disk groups, you must ensure that the disks that contain their DCO plexes can accompany them. You can use storage attributes to specify which disks to use for the DCO plexes. (If you do not want to use dirty region logging (DRL) with a volume, you can specify the same disks as those on which the volume is configured, assuming that space is available on the disks). For example, to add a DCO object and mirrored DCO volume with plexes on disk05 and disk06 to the volume, myvol, use the following command:

#vxsnap -g mydg prepare myvol ndcomirs=2 alloc=disk05,disk06

To view the details of the DCO object and DCO volume that are associated with a volume, use the vxprint command. The following is example vxprint -vhoutput for the volume named vol1 (the TUTIL0 and PUTIL0 columns are omitted for clarity):

TY

NAME

ASSOC

KSTATE

LENGTH

PLOFFS

STATE

...

v

vol1

fsgen

ENABLED

1024

-

ACTIVE

 

pl

vol1-01

vol1

ENABLED

1024

-

ACTIVE

 

sd

disk01-01

vol1-01

ENABLED

1024

0

-

 

pl

foo-02

vol1

ENABLED

1024

-

ACTIVE

 

sd

disk02-01

vol1-02

ENABLED

1024

0

-

 

dc

vol1_dco

vol1

-

-

-

-

 

v

vol1_dcl

gen

ENABLED

132

-

ACTIVE

 

pl

vol1_dcl-01

vol1_dcl

ENABLED

132

-

ACTIVE

 

sd

disk03-01

vol1_dcl-01 ENABLED

132

0

-

 

pl

vol1_dcl-02

vol1_dcl

ENABLED

132

-

ACTIVE

 

sd

disk04-01

vol1_dcl-02 ENABLED

132

0

-

 

In this output, the DCO object is shown as vol1_dco, and the DCO volume as vol1_dcl with 2 plexes, vol1_dcl-01and vol1_dcl-02.

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HP Veritas Volume Manager 5.0 -UX 11i v3 manual Specifying storage for version 20 DCO plexes