Life after Disaster, Not beyond Repair

When evaluating potential solutions for enterprise environments, many administrators reject ostensibly "cool" products out of hand. That was our temptation when we sat down to review ERDisk 5.0, a disaster recovery solution from Aelita Software Corp. ( The product's premise -- which purports to automate the tedious task of creating Windows NT emergency repair disks (ERD) -- was as cool as they come, and its proposed application intriguing. Such a "cool" product couldn’t effectively double as a practical, real-world solution, could it?

Windows NT 4 ERD always seemed something of an aberration -- an ill-advised attempt to provide enterprise-class disaster recovery for Windows NT systems. As experience demonstrated time and again, updating ERDs, storing ERD disk images, and physically applying ERDs to affected clients was more trouble than it was worth.

If a product such as ERDisk 5.0 is to work, it must demonstrate compelling value over Windows NT/2000’s generic backup solution, as well as competing solutions such as Ghost from Symantec Corp. ( -- which creates images of hard disk environments that can be restored in the event of corruption or system failure.

ERDisk 5.0 works by copying emergency repair information from Windows NT 4.0 and Windows 2000 clients and servers across a network to a centralized storage location. It is from the central data store that remote restore procedures can commence, emergency repair disks can be created, and advanced ERD recovery sessions can be facilitated.

ERDisk 5.0 can run natively on client machines -- in which case raw, uncompressed data is sent over the network to a central data store -- or can use distributed collection agents, which can compress backup data before sending it over the wire.

ERDisk 5.0 in Action

ERDisk 5.0 provides three restore options from which to choose.

The first, a remote restore feature, allowed us to repair failed Windows NT and Windows 2000 Professional installations remotely. If we wanted to use its remote restore mode, however, we had to make sure we were still in a Windows NT or Windows 2000 system with network support. Dead or unbootable systems and clients not attached to the network cannot be resuscitated in this manner.

To perform restoration tasks in the ERDisk 5.0 environment, you have to bring up the ITS repair wizard. ITS is a GUI-based tool that helps the user select the computer to repair, allows the user to choose the particular restoration method, and lets the user specify if he or she wants to restore an entire system registry or a number of individual hives within a registry.

In the case of remote restore, ERDisk 5.0’s ability to restore individual hives proved to be particularly beneficial. It allowed us to back out of a problematic software installation without going through the time and trouble of restoring the entire operating system environment itself. Being able to do so over the network was a nice touch, as well. After removing all traces of a pesky antivirus software program that caused a number of anomalies on our test Windows 2000 Professional client, the machine rebooted and functioned as normal.

ERDisk 5.0's second restore option features a Windows NT ERD ability that allowed us to create a standard Windows NT 4.0 ERD to resuscitate a failed system. Distinct from the basic Windows NT 4.0 ERD creation scenario, the ITS repair wizard let us specify which registry hives we wanted to place on our disk.

After we created our Windows NT 4.0-compatible ERD, we were able to boot the damaged test client -- using either a Windows NT 4.0 CD-ROM or the Windows NT 4.0 boot floppies -- and restore the damaged Windows NT 4.0 environment to a functional state. For the purposes of our test, we removed the all-important HAL.DLL file -- which rendered the test client unbootable -- and deleted the system hive. ERDisk 5.0’s NT ERD feature restored both to functionality, exactly as a native NT ERD would have done. ERDisk 5.0’s Windows NT 4.0 ERD restored the system to normal operation.

Finally, ERDisk features a true disaster recovery restoration method, dubbed the Advanced Aelita ERD. This feature offers a functional enhancement over its two other restoration modes. The Advanced Aelita ERD purports to be able to restore unbootable Windows NT 4.0 or Windows 2000 Professional installations, and to be able to replace any amount of missing data on a damaged hard disk.

Advanced Aelita ERD is enabled by ERDisk’s emergency repair console, a command-line environment that is used in the absence of a bootable operating system environment. Using ERDisk’s Repair Wizard, we were able to create a set of boot floppies that we used to regain access to the hard drive of a failed Windows NT 4.0 client.

In this particular case, we backed-up our test Windows NT client’s entire system registry onto CD-R and then deleted it. ERDisk 5.0’s Advanced Aelita ERD restoration method let us restore the missing registry, and our Windows NT 4.0 client booted as normal.


ERDisk 5.0 provides a distinct advantage over Windows NT’s and Windows 2000’s native backup/restore capabilities, as well as over disk imaging products such as Symantec’s Ghost. ERDisk can, for example, facilitate the incremental updating of ERD data from distributed Windows NT and Windows 2000 clients, and can also restore entire system environments. Because changes are squirted across the network as they happen, and because its agents can compress data before it is sent over the wire, the solution is not a bandwidth hog.

It is often impractical or impossible to update system environment settings as often as one would like when using a disk-imaging product such as Ghost, but it’s an inherently network-intensive practice, as well.

Windows 2000 ships with several recovery features, including a command-line recovery console and a system state backup feature. ERDisk 5.0’s advantage isn’t as pronounced when deploying it in conjunction with Windows 2000 systems, but it can provide a value-add. Windows 2000’s system state backup, for example, often requires more than 200 MB of storage space; an ERDisk backup can sometimes fit on a single floppy disk.

Some of ERDisk 5.0’s features can be found separately in Microsoft product offerings. Its ability to restore registry settings at the hive level, for example, apparently leverages an API similar to that used by the Windows NT 4.0 Resource Kit’s REG.EXE command.

All things considered, ERDisk 5.0 brings premium features and functionality together under one common administrative hood. It’s a cool product, to be sure, and one that is fit for the enterprise.

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