HP Serviceguard Extension for RAC (SGeRAC) Creating Mirrored Logical Volumes for RAC Data Files

Logical volume “/dev/vg_rac/redo1.log” has been successfully created with character device “/dev/vg_rac/rredo1.log”

Logical volume “/dev/vg_rac/redo1.log” has been successfully extended

NOTE: With LVM 2.1 and above, mirror write cache (MWC) recovery can be set to ON for RAC Redo Logs and Control Files volumes. Example:

# lvcreate -m 1 -M y -s g -n redo1.log -L 408 /dev/vg_rac

NOTE: The character device file name (also called the raw logical volume name) is used by the Oracle DBA in building the RAC database.

Creating Mirrored Logical Volumes for RAC Data Files

Following a system crash, the mirrored logical volumes need to be resynchronized, which is known as “resilvering.”

On node and cluster-wide failures, when SLVM mirroring is used and Oracle resilvering is available, the recommendation is no mirror resynchronization (NONE) for the datafiles because Oracle would perform resilvering on the datafiles based on the redo log.

If Oracle resilvering is not available, the mirror recovery policy should be set to either full mirror resynchronization (NOMWC) or fast resynchronization (MWC) . For more information on using NOMWC and MWC, refer to the HP-UX System Administrator's Guide: Logical Volume Management HP-UX 11i Version 3 on www.hp.com/go/hpux-core-docs —> HP-UX 11i v3.

In the case Oracle “resilvering” is not available, create logical volumes for use as Oracle data files by using the same options as in the following:

Example for “NOMWC”:

# lvcreate -m 1 -M n -c y -s g -n system.dbf -L 408 /dev/vg_rac

•-m1—Specifies single mirroring.

•-Mn—Ensures that mirror write cache recovery is set to OFF.

•-cy—Mirror consistency recovery is enabled.

•-sg—Mirroring is PVG-strict. It occurs between different physical volume groups.

•-nsystem.dbf—Specify the name of the logical volume.

•-L408—Allocates 408 megabytes.

Example for “MWC”

# lvcreate -m 1 -M y -s g -n system.dbf -L 408 dev/vg_rac

The -M y option ensures that mirror write cache recovery is set ON.

NOTE: Contact Oracle to determine if your version of Oracle RAC allows “resilvering” and to appropriately configure the mirror consistency recovery policy for your logical volumes.

In the case Oracle “resilvering” is available, create logical volumes for use as Oracle data files by using the same options as in the following example:

# lvcreate -m 1 -M n -c n -s g -n system.dbf -L 408 /dev/vg_rac

•-m1—Specifies single mirroring.

•-Mn—Ensures that mirror write cache recovery is set to OFF.

•-cn—Mirror consistency recovery is disabled.

•-sg—Mirroring is PVG-strict. It occurs between different physical volume groups.

•-nsystem.dbf—Specify the name of the logical volume.

•-L408—Allocates 408 megabytes.

If the command is successful, the system will display messages like the following:

Creating a Storage Infrastructure with LVM 43