Purpose of ERD

I'm wondering what the purpose of creating an ERD with NTBackup on a Windows 2000 server would be.  We currently use Veritas 9.1 to backup our servers nightly so NTBackup is not our normal method.  I understand that an ERD can let you boot a system if something goes wrong with your hard drive but I fail to understand exactly what it does and what it lets you do.  Also, if we are using Veritas, do I need an NTBackup ERD or is there some equivalent in Veritas?  

How often do you create ERDs if ever?
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Lee W, MVPTechnology and Business Process AdvisorCommented:
If you're backing up the system state in Veritas, then you don't really need an ERD in my opinion.  It's effectively a registry and SAM backup.  I don't usually rely on tape backup though for this purpose, I usually make the ERD (registry backup) periodically leaving it in a state that I can manually recover a hive if necessary.
Eagle6990Author Commented:
Well, after I typed this I checked my Veritas info about ERD and found this.

Creating an Emergency Repair Disk
When Windows NT or Windows 2000 Server is installed, the installation program prompts you to create an Emergency Repair Disk (ERD). This disk contains system information that can help get the system running in the event of a disaster. It is important to keep the ERD updated whenever system changes are made. The ERD is only useful if it is kept current.

For Windows XP or Windows Server 2003, Emergency Repair Disk has been replaced with Automated System Recovery (ASR).

Whenever a major change is made to the system, make a fresh copy of the ERD before and after the change is made. Major changes include adding, removing, or otherwise modifying hard drives or partitions, file systems, configurations, and so forth. As a general rule, update the ERD before and after the hard drive configuration is changed. The addition of a new component to the server, such as Microsoft Exchange Server or Microsoft SQL Server, and changes from Control Panel, are also situations in which the ERD should be refreshed both before and after the change.

Also remember to make a backup of the ERD; always keep an ERD from at least one generation back. When creating a fresh ERD, use a floppy disk that can be reformatted, because RDISK.EXE, the program that creates the ERD, always formats the floppy disk.

So I guess my real question is, has an ERD ever saved you and how?  Seems like a lot of work to keep 2 generations of ERD for my 15 servers, all on floppy, for something that "Last Known Good" should be able to take care of.
Lee W, MVPTechnology and Business Process AdvisorCommented:
The disk itself has been essentially useless since I learned exactly what it did.  A ERD basically sets up a floppy so that the repair process knows where the OS is and where the repair info is.  Unless you make one, I've not found (nor really looked) for a way to backup the lkey registry files.  When you create the repair disk, it copies the regsitry files to c:\winnt\repair - if you ever have registry corruption, you can then boot system and copy the good files in repair to the bad files in config.  I've done this a number of times.

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It saved us from having to reinstall the OS (it wasn't bootable before using the ERD disks). If you have to get a veritas backup restored, you generally have to get veritas running again before, which could mean installing the OS plus the backup software. and probably also some service packs.
Eagle6990Author Commented:
Thanks everyone.  I went ahead and created the ERD but I'm glad to know about the registry backup to the repair folder as well.
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