Installation guide

Because it supports larger volumes, parted is the recommended tool to create partitions on Red Hat Enter-

prise Linux 5.

The disk management utilities for x86/x86_64 based systems generally write 63 sectors of metadata (msdos la-

bel or partition table) directly at the beginning of the LUN. The addressable space begins immediately after

these initial sectors causing a misalignment with the RAID strips and, as a result, excessive cross disk accesses

leading to performance degradation.

To avoid this issue, the partition should be aligned so that its data space starts on the same sector where RAID

stripe begins. For example, if the CLARiiON array has 64KB striping, the first writable sector of the partition

should be sector 128 (128 * 512 bytes = 64KB). Below is an example of how to create a partition on a CLARi-

iON storage array using parted utility. It is assumed that the LUN is available through the device-mapper-

multipath as device /dev/mapper/asm1.

# /sbin/parted /dev/mapper/asm1 mklabel msdos unit s mkpart primary “128 -1”

Information: Don't forget to update /etc/fstab, if necessary.

Check the results:

# /sbin/parted /dev/mapper/asm1 unit s print

Model: Linux device-mapper (dm)

Disk /dev/mapper/asm1: 251658239s

Sector size (logical/physical): 512B/512B

Partition Table: msdos

Number Start End Size Type File system Flags

1 128s 251658224s 251658097s primary

Information: Don't forget to update /etc/fstab, if necessary.

Configuring Raw Devices for Oracle 10g RAC

Oracle RAC 10g R2 can be installed with Clusterware 10.2.0 or 11.1. Oracle Universal Installer for Oracle 10g

R2 RAC can't verify visibility of Clusterware devices from all cluster nodes unless they are raw devices. As a

result, the installation of Clusterware 10.2.0 requires raw devices. Oracle 10g R2 database server and ASM do

not require raw devices but can use them. Starting from Oracle 11g Release 1, Clusterware files can be placed

on either block or raw devices located on shared disk partitions. Using Cluserware 11.1 with Oracle RAC 10g

R2 is simpler because it does not require raw devices. Nevertheless, below we are describing how to configure

raw devices with single path and multipath LUNs.

Let us assume that the LUNs have been created on a supported shared storage, appropriately sized, partitioned,

and visible from all cluster nodes. In multipath setup, the same LUN is visible several times and the operating

system creates a separate SCSI device (/dev/sd*) for each path.

1. Verify visibility of the Clusterware devices and partitions:

# cat /proc/partitions

Partitions on the Clusterware devices may be not visible if they have been created on another cluster node or on

iSCSI target. In this case, re-read the partitions with /bin/partprobe <device>.