Plan for the worst, hope for the best: backup & disaster recovery, Part 2

Computer Technology Review, April, 2004 by Morgan Edwards

In March CTR, Part 1 stressed the importance of regular periodic backups with disaster prevention in mind, and a focus on the ultimate goal of disaster recovery while implementing a plan for disaster prevention.

Hardware

The device selected for backup is fundamental to any successful plan. In the old days, minicomputer user's choices were limited to using relatively small removable disk and open reel tape (first 1600bpi & then 6250bpi drives). In today's backup landscape, while there are many more devices to choose from, the same old conundrum applies as back in the early days--spend a lot to get the best, or buy a cheaper alternative and potentially pay the price in other ways. Bottom line, the device needs to be of sufficient size and speed to allow a full system backup in a reasonable period of time. Choices for users have expanded over the years from single tape QIC, 4MM and 8MM drives, to DAT5, AIT, Super DLT and LTO2 drives, in single unit or autoloader configurations, that offer mind boggling capacities and speeds when compared to what was available even five years ago.

A good example of the latest and greatest hardware is the pending release of a new LTO2 drive slated for this summer with a native capacity of 400GB on a single tape. As usual, this drive will have built-in compression logic and will be quoted (using 2:1 compression) as a 800GB capacity drive. Whether 400 or 800, the amount of data stored on a single tape is now astounding. Furthermore, I've found in our own lab that the LTO2 drive backs up routinely anywhere between 300MB/minute to 2GB/minute. The speed is directly related to whether the backup is a standard file-by-file network backup or a higher speed image backup. For those who don't know, image-based backups are the absolute fastest means of backing up and restoring a partition or disk.

Just for grins, let me compare the LTO2 of today against the first 8MM device released on Wang's VS minicomputer (my market before entering Windows). When Wang initially released the WUBU (Wang Unattended Backup Unit) using an Exabyte 8200 it cost about $20,000 for an 8MM tape, holding a little over 2GB, with a backup rate of about 400-600MB per hour. Fast-forward to today and compare that Stone Age device to a hot Super DLT or LTO2 drive that easily backs up at rates of 400-600MB per minute--and at a fraction of the cost!

For smaller users, the name of the game is still 4MM DDS-5 drives with 36GB native capacity. Such drives offer capacity, speed, and economy, to thousands of users of small to medium size networks. 4MM based autoloaders offer even greater economy of scale. Today's state of the art drives are so fast that keeping them streaming at a high rate of speed can be difficult and requires both a fast system and efficient software.

Most organizations find this a luxury, but as a prudent investment, I always recommend buying a second tape drive. A second tape drive is inexpensive and can be used as a secondary backup unit in case the primary drive fails. It can also be used to either duplicate nightly backup tapes and/or automatically cascade full tapes (if appropriate software is purchased). Duplicating a backup tape for off-site storage is a key disaster prevention method and can be implemented either through optional hardware or software. If you are not practicing off-site media storage, you are proverbially placing all your eggs in one basket. A single event like a fire could destroy every onsite backup, with the likely result of also destroying your ability to recover your business from being wiped out by the catastrophe.

Software

While perhaps not as obvious initially, the software selected for backup and disaster recovery is equally important as the hardware selected. The software should be fast, secure, have all the necessary features, and be extremely reliable. The company behind the software is also an important element in the selection process

The accessibility and the quality of support from your selected software provider can make all the difference. Whether working through problems created by hardware or software, operational errors, network issues, or security/permissions problems, there is no substitute for experienced and timely technical support. In my experience, well over half of the technical support calls made by customers with problems really have nothing to do with the backup software, so it is extremely important that technical support people be well versed in everything to do with backup and recovery.

At a minimum, software selected for backup should provide fast, reliable backup, verify, and restore operation. Other desirable software features include protecting data tapes from being overwritten, hardware error trapping and reporting, email alerts, operator prompts and messages, tape cascading, hardware failure redirect, tape duplication, and restore logic which attempts to recover from bad tapes.

It is also important to be aware that there are really two types of backups. The standard file-by-file method backs up and restores function through a machine's operating system. Image backups and restores work on a lower level and bypass a machine's OS. Both types of software offer key benefits. File based backups allow full, incremental, and differential backups. It also typically offers extensive file selection logic to include or exclude files from backup. Image backups are low level and typically backup an entire partition or disk. These backups are fast, and are designed to work in conjunction with special boot media to quickly restore a partition (like an operating system) on an unbootable machine in the shortest amount of time. This type of software is frequently called "Bare Metal Restore" for its ability to boot a dead machine and bring it back online with minimal time and effort. Both file and image-based backups offer unique benefits, and many users are finding it prudent to incorporate both methods into their daily backup regimes. While not pervasive today, I predict that in three to five years image-based backup will be considered "must-have" software.