Dynamic Root Disk: Quick Start & Best Practices

same time, verify that System Fault Manager (SFM) and Event Monitoring Service (EMS) are

installed and configured properly.

Adjusting File System Sizes on the Clone

In Step 3 above, the output of the update-ux -p command will identify file systems that need to be

expanded, and these changes can be made on the clone prior to activating it and performing the

actual update. You can find detailed information on how to expand file systems, including /stand,

later in this whitepaper’s Using DRD to Expand LVM Logical Volumes and File Systems section.

Special Considerations with Different OS Versions on the Active and In-Active Images

After Step 5 is executed, the clone (disk 5) becomes the active disk, and the original disk (disk 1)

becomes inactive. Both disks are still running HP-UX 11i v2. After Step 6 is executed, the active disk

is running HP-UX 11i v3, and the inactive disk is running HP-UX 11i v2. Whenever you are in a

situation where the active and inactive disks are not running the same major release of HP-UX, you

need to be aware of some limitations:

• If an HP-UX 11i v2 disk is booted and HP-UX 11 v3 is on the inactive clone, you should not use any

sw* commands with drd runcmd.

• If an HP-UX 11i v3 disk is booted and HP-UX 11i v2 is on the inactive clone, you can run drd

runcmd swlist or drd runcmd swverify; however, you cannot run any other

sw*commands.

Best Practice 5 (BP5): Basic Recovery

A key benefit of the DRD toolset is that you can use it for basic system recovery. While mirroring

provides excellent up-to-date protection from hardware failures, the clone can provide a fallback for

reverting from recent software changes. Disk mirroring provides robust protection against hardware

failures, but it also automatically updates the mirror image with all software and file system updates.

Therefore, if a software installation caused an undesirable system state, DRD provides a better

mechanism for quickly returning to the system’s previous state. For this scenario, our setup is as

follows:

Original image: /dev/disk/disk1

Clone disk: /dev/disk/disk5

Change to be made: Modify semaphore tunables prior to updating an application

Objective: Utilize a DRD clone as a quick recovery mechanism for the root volume group if needed.

BP5: Overview of Steps

1. Create the clone: drd clone –t /dev/disk/disk5

2. Use drd status to view the clone: drd status

3. Modify semaphore tunables in preparation for updating an application

4. Create a shutdown script that runs drd sync so that files changed on the original image after

the clone was created will be propagated to the clone (see the “DRD sync” section below for more

details)

5. While making the tunable changes, a critical networking configuration file is accidentally deleted,

so we need to activate and boot the clone which contains the original image:

6. drd activate -x reboot=true