rhel asmlib to_udev

How to Replace ASMlib with the udev Device Manager

for New and Existing Oracle Instances Author: Jason GanovskyEditor: Allison Pranger05/11/2011

PURPOSE AND OVERVIEWOracle recently announced that ASMlib will not be certified or supported on Red Hat Enterprise Linux 6.

Oracle has indicated that all other major components of the Oracle database stack, including ASM and RAC,

will be supported on Red Hat Enterprise Linux 6 moving forward, and the certification process is currently

underway.

Udev is a native component of Red Hat Enterprise Linux and as such is fully supported by Red Hat. Oracle

has published several white papers and technical guides on configuring their database with udev-managed

devices, demonstrating their support for the technology as well.

The purpose of this document is to explain how the udev device manager can be used to replace ASMlib

for ASM-backed Oracle instances. This document attempts to bridge the gap for those familiar with either

udev or ASMlib, but not necessarily with both. Additionally, it details how to create new ASM disk groups

from scratch using udev and explains how to perform an in-place migration from an ASMlib implementation

on Red Hat Enterprise Linux 5 to an equivalent, supported udev configuration without requiring any re-

installation or re-configuration of database components.

SETTING UP ASMLIB FOR ASM ON RED HAT ENTERPRISE LINUX 5

In order to understand how ASMlib works and what it does in terms of server configuration, a detailed

ASMlib setup is outlined below.

1. Install the relevant ASMlib components for your operating system/kernel combination.

How to Replace ASMlib with the udev Device Manager for New and Existing Oracle Instances | Jason Ganovsky 1

2. Run /etc/init.d/oracleasm configure and assign the appropriate environment variables.

NOTE: Creating new ASM disks will fail if you use non-standard Oracle user/group names and fail to specify them correctly here.

3. Run /etc/init.d/oracleasm createdisk for each partition that will be assigned to a disk

group.

4. Note that Oracle creates new device entries under /dev/oracleasm/disks for each disk

created. The key benefits of ASMlib are that it creates consistent device names, assigns the

correct user/group ownership for files (dbauser/dbagroup), and assigns the correct permissions

(660).


CONFIGURING UDEV FOR ASM ON RED HAT ENTERPRISE LINUX 5

This section provides background information for a later section, Moving from ASMlib to udev on a Running

Oracle Server, which explains how to change ASMlib-tagged disks to udev-managed devices.

The steps below describe how to create udev rules for new disk groups for use by ASM.

1. Each SCSI block device is assigned a unique identifier that is used as the basis for udev device

rules. To obtain this identifier, run the following command for each SCSI block device that will be

used as part of an ASM disk group: scsi_id -g -u -s /block/sdx, where sdx represents an

appropriate block device, such as /block/sdb.

2. Create a new udev rules file in /etc/udev/rules.d using the unique identifiers obtained in step

1. Udev will use this configuration file to create persistent/consistent device names, assign the

correct ownership for your Oracle operating system user and group (typically oracle and dba

respectively, or oracle and oracle in this example), and assign the correct rights to those users

(rw for the block device or 0660). Give the new rules file a name that identifies it as ASM specific,

(for example, /etc/udev/rules.d/99-asm.rules) using the following template for each block

device:

KERNEL=="sd*", BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -s %p", RESULT=="insert-uuid-from-step-1-here", NAME+="oracleasm/disks/DSK#" OWNER="linux-oracle-user" GROUP="linux-oracle-group" MODE="0660"

3. Reboot or run start_udev and verify that all entries have been properly created in

/dev/oracleasm/disks. Also, verify that your Oracle Linux user and group have ownership of

all devices to be used with ASM and that the permissions are set to 0660.


4. Continue with the next section to configure ASM on Red Hat Enterprise Linux 5.

CONFIGURING ASM ON RED HAT ENTERPRISE LINUX 5

Regardless of whether you used udev or ASMlib to create persistent device names and set up the

appropriate block-device permissions, you can use the following steps to configure Oracle ASM on Red Hat

Enterprise Linux 5.

1. Prior to configuring ASM, you must set up CSS. Run $ORACLE_HOME/bin/localconfig add as

root.

2. As the Oracle operating system user, run dbca to configure ASM storage.


3. Select Configure Automatic Storage Management and click Next.

4. Configure a new ASM SYS user password (for consistency, you can use the existing SYS

password) and click Next.


5. Click Create New.

6. Give the disk group a name and select all available disks.

NOTE: It might be required to click Change Disk Discovery Path and point to /dev/oracleasm/disks/* in order for Oracle to recognize the appropriate block devices.


7. Click Finish.

8. Click Yes to perform another operation.

9. Select Create a Database and click Next.

10. Select General Purpose and click Next.


11. Name the database asmdb and click Next.

12. Deselect Configure Enterprise Manager and click Next.


13. Choose passwords for SYS/SYSTEM and click Next.

14. Select ASM for storage and click Next.


15. Select the newly created disk group and click Next.

16. Select Oracle Managed Files and click Next.


17. Deselect Specify Flash Recovery Area and click Next.

18. Do not select Sample Schemas and click Next.


19. Use the default settings for memory, sizing, character sets, and connection mode and click Next.

20. Use the default security settings and click Next.


21. Deselect Enable Automatic Maintenance and click Next.

22. Click Finish.

23. Click OK.


MOVING FROM ASMLIB TO UDEV ON A RUNNING ORACLE SERVER

This section assumes that you have already set up and configured ASM and ASMlib and that they are

hosting databases.

In the following example, a database named newdb is running on ASM disk group DG1, which is backed by

ASMlib-managed devices. DG1 comprises partitions /dev/sdb1, /dev/sdc1, and /dev/sdd1 mapped to

ASM DSK1, DSK2, and DSK3 respectively.

1. Shut down all Oracle database services and ensure the ASM disk group is unmounted.


2. Shut down and disable the ASM service. To ensure the integrity of the disk-group data, the server

should be rebooted and you should verify that /dev/oracleasm no longer exists before

continuing.

3. Configure /etc/udev/rules.d/99-asm.rules as noted in the section Configuring udev for

ASM on Red Hat Enterprise Linux 5.


4. Run start_udev or reboot the server and verify that the /dev/oracleasm/disk entries are in

place.

5. Verify that ASM starts and the disk group mounts properly.

6. Verify that the ASM-backed database starts properly.


At this point, ASMlib has been replaced by udev for the specified disk group.


Copyright © 2011 Red Hat, Inc. “Red Hat,” Red Hat Linux, the Red Hat “Shadowman” logo, and the products listed are trademarks of Red Hat, Inc., registered in the U.S. and other countries. Linux® is the registered trademark of Linus Torvalds in the U.S. and other countries.

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