Friday, June 22, 2012

Dynamic Root Disk (DRD)

DRD Concepts : -
Minimizing Downtime with Dynamic Root Disk



HP's Dynamic Root Disk (DRD) product is a new tool that enables software maintenance and recovery on an HP-UX operating system with minimum system down time. Using DRD, you can easily and safely copy a system image from vg00 to a "clone" volume group.

DRD ensures that the clone volume group's LVM structure, file systmes, files, and directories are identical to the original volume group. If the original boot disk is mirrored, DRD can optionally create a mirror in the clone volume group, too.

When the administrator installs software or patches, or modifies configuration files on the active boot disk, the clone remains unchanged.

DRD clone functionality can potentially decrease both planned and unplanned downtime.



DRD Benefit: Minimizing Unplanned Downtime:

Most HP-UX administrators implement disk mirroring to protect against disk hardware failures. However, a careless typo by a system administrator, security breaches, and critical software defects could corrupt both mirrors. In some cases, the administrator can only recover by booting from a system recovery tape, which requires system downtime.

If the failed system has a DRD clone, the administrator can simply activate and boot the DRD clone, which requires much less downtime.



DRD Benefit: Minimizing Planned Downtime:

Installing software and patches sometimes requires system downtime.

Using DRD commands, you can apply patches, install software products and make other modifications to the cloned system image without affecting the active system image. Then during the next convenient maintenance window, reboot the system from the patched/cloned system image with very minimal downtime. If the patches cause problems for applications, simply reboot using the original disk.



DRD Rehosting:

All DRD functionality, with the exception of rehosting, is now supported on HP-UX 11iv3 systems using VxVM 5.0 root volumes.



Creating and Updating a Clone:


If you have the MirroDisk/UX license, you can create a mirrored clone.

DRD also supports cloning of a VxVM root on HP-UX 11i v3.



Accessing Inactive Images via DRD-Safe Commands:

Administrators can execute commands on the inactive image via the drd runcmd
utility. DRD includes safeguards to ensure that commands executed via this utility never affect the
active system image. drd runcmd can only be used to execute "DRD-Safe" commands.
Attempts to use drd runcmd to execute commands that aren't DRD-Safe fail.
The current DRD-Safe list includes nine commands:

* swinstall
* swremove
* swlist
* swmodify
* swverify
* swjob
* kctune
* update-ux
* view




Activating an Inactive Image:

The administrator can use the drd activate command to reboot the system using the inactive system image at any time. Booting from the inactive system image offers a number of benefits:

* If accidental or intentional changes to the active system image cause problems, boot from the inactive image to restore system functionality without a time consuming tape restore.

* After installing patches on the inactive system image with drd runcmd swinstall, activate the inactive system image during the next maintenance window to make the new patches take effect.