Comparing host-based D2D to VTLs for backup and restore: Part 1

Computer Technology Review,  Sept, 2004  by Paul Feresten

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Tape technologies have been the dominant force in backup and recovery almost since the beginning of modern computing; however, the landscape is finally changing. With the arrival of next-generation ATA disk technology, newer, low-cost backup and recovery methods are being offered by vendors promising to solve many of the problems that IT administrators have faced with tape backups and restores. The market has produced a proliferation of disk-based offerings ranging from simply including disk arrays as a "middleman" in the backup path to complicated imaging and snapshot systems that store their content on disk. With such a wide field of offerings, it is useful to focus in on only a couple at a time and see how they compare. In this discussion, we will take a closer look at two of the most promising of these new backup technologies, namely host-based disk-to-disk (D2D) and virtual tape libraries (VTL).

At the outset, new host-based D2D backup strategies using ATA disk arrays seemed to offer the most promise, using low-cost disks and providing increased data transfer speeds for backup and recovery. As many IT administrators rushed to implement D2D, they discovered that there are a number of challenges with D2D that may not have been readily apparent, including integration issues, storage formats, file system size and performance problems, fragmentation concerns and others. IT administrators should be aware of these issues as they strive to reap the benefits of D2D in their backup and restore environments.

Another technology that is capturing the attention of IT administrators is that of virtual tape libraries (VTLs). VTL takes elements from both traditional tape backup and the newer ATA disk-based technology and combines them to provide a solution optimized for existing backup environments. A virtual tape library is essentially a disk-based library that emulates standard tape library and tape formats. Acting like a tape library in the environment, with the performance of modern ATA disk, this new VTL is truly the "best of both worlds".

Here, we will first take a look at the problem of traditional backup and restore from tape, another quick look at the advent of ATA technology, then delve deeper into these two new backup and restore technologies. We will investigate the benefits and challenges of each technology and present information that will help executives and IT decision makers determine which is the better technology to improve their backup environment.

The Nightmare of Traditional Tape Backup and Restore

Backup and restore from tape has been a source of consternation for IT administrators for years. One has only to make a quick search of the Internet for the topic "tape backup problems" to see the proliferation of articles and discussions about the challenges of traditional tape backups. After looking at some of the top entries, some of the problems described include:

* Tape failures during backup

* Failed notifications of incomplete backups

* Inability to locate an appropriate and current backup tape

* Cost of tape media

* Tape backup overruns into production time

* Inadequate restore speeds from tape

In spite of all of these difficulties, organizations have been left with few alternatives to traditional backup technologies until recently. To add to the list of common problems with tape backup and restore, IT administrators are now faced with a growing mountain of data that must be protected.

Improvements in computing hardware--like processor and memory speeds, lower cost hardware and software, and application development advances that improve computing capabilities--have led to the creation of more (and larger) data. Historically, data consisted primarily of text, word processor documents, spreadsheets and the like. The total amounts of data created in an organization were relatively small in size and were not very difficult to backup and restore using tape media. Today organizations use more complex applications to create images, databases, 3D geophysical maps, movies and other sizeable data. The total quantity of this data within organizations has become rather daunting for IT administrators, and is increasingly difficult to manage in terms of tape backup and recovery following data corruption or system failures.

Over the past few years, IT administrators have begun to look to disk-based solutions to solve the nightmares of tape backup and recovery. The most prevalent problem with implementing disk-based systems has been the cost of hard drives in comparison to tape media. In order to utilize a disk-based solution, IT administrators were often faced with doubling their total disk capacity to create an online backup, yet still having to further backup to tape for a complete data protection scenario. This approach would solve the problem of backup overruns and tape restore speeds, but still carried a cost that was typically insurmountable. These nightmares of traditional backup soon set the stage for new technology that could offer the data protection of tape, the performance of disk, at a cost that was still in that same ballpark as the tape technology.