Data Centers

How to build a scalable backup solution

Organizations tend to go through two or three phases in regard to backup solutions as their networks grow. However, this doesn't mean you have to toss out the old tape system when you bring in the new disk-based one – a scalable long-term backup plan lets you integrate the two and enjoy the best of both worlds.

Many IT professionals see backup solutions as a necessary evil, sort of like buying insurance. You hope you'll never have to use it, and if you don't, you may think of the money you spend on it as wasted. But you don't dare go without it.

Your backup solution isn't out there saving you from a dire fate every day like a firewall. It doesn't provide a dramatic improvement in performance or user productivity. It's just there â€" until you need it. Then it's priceless.

From disk to tape

When your business is small, the easiest (and least expensive) way to back up your data may be to use a program such as Second Copy to run in the background and make a copy of your data files to another location, such as another server on the network. Because the backup of the data is on disk, it's fast and easy to retrieve it.

As the organization grows and begins to accumulate more and more data, it's common to switch to a tape backup solution. The low cost of tape, as well as the ease with which it can be stored off-site to guard against having the backup destroyed along with the originals in case of a natural disaster, make it an attractive option. You can get autoloaders that do away with the need to manually insert tape cartridges into individual tape drives.

The problem is that tape drives, especially of the standalone variety, become more and more inefficient once you surpass a certain amount of data. Robotic tape library systems can be a solution, but they're costly (often tens of thousands of dollars). What's the difference between an autoloader and a robotic library? The autoloader contains one tape drive and multiple slots for tape cartridges (typically 10 or fewer). A library system encompasses multiple drives and a number of locations for cartridges.

And back to disk

While tape has been the backup medium of choice for large organizations for years, a recent trend as the organization grows bigger still is to return to disk-based backup, but with a difference. Disk-based backup solutions for the enterprise are far more sophisticated than the simple scheduled copying programs used by smaller businesses, but they can also be costly.

One advantage of disk over tape is speed of access. You have to search through a tape from the beginning to find a particular block of data , while the heads on a disk drive can go directly to a particular place on the disk.

Disks also tend to be more reliable than tape. Most users of tape backups have had the experience of a backup or recovery failure; some estimates put the failure rate at 20 percent or more. Even worse, you often don't know that a backup has failed, or partially failed, until you need it.

The move from tape back to disk is based in part on the falling prices for high capacity hard disks, and in part on the difficulty of managing and rotating the large number of tapes required in the enterprise environment.

Disk-based options

Hardware based disk backup solutions (disk-to-disk appliances) are available from a number of vendors, but often cost $50,000 or more. These "turn key" solutions are relatively easy to implement, but as with most appliance-style devices, they're usually more difficult to expand or upgrade and limit you to their built-in features.

There are also software based solutions, such as Microsoft's Data Protection Manager (DPM), that run on standard network operating systems and PC hardware. (Data Protection Manager is still in beta testing. It's expected to be available in the second half of 2005.)

One important feature of DPM is the ability to allow end users to recover their own files, without having to go through the IT department. This can greatly reduce IT administrative overhead (and frustration) on those occasions when users accidentally delete or "lose" their files. Another advantage of these solutions is the ability to back up your data continuously, instead of the usual once-per-day (or less) schedule.

Another software product is UltraBac, which allows you to make image backups to either disk or tape and works with a companion program, UltraCopy, that makes it easy to copy disk-based backups to tape.

Disk-based backups can be divided into two basic types:

  • Disk-to-disk (D2D)
  • Virtual tape (VT)

Virtual tape systems storage backups on disk but emulate tape drives and formats, letting administrators use the backup processes with which they're already familiar, while gaining the performance advantage of disks. To the operating system, the disk-based backup appears to be a tape library.

Creating a scalable backup plan

If you're charged with implementing a backup solution for a small but growing business, must you go through the process of moving from low-cost disk backup programs to tapes and then back to high-end disk-based solutions, or can you plan your backup strategy to scale as the company grows?

The good news is that tape and disk are not mutually exclusive. Many companies are enjoying the "best of both worlds" by combining disk-based backups with long-term archives stored on tape. This type of tiered backup strategy not only takes advantage of the disk's speed of access for immediate retrieval and tape's flexibility for off-site storage, it also makes it easy for you to scale your backup solution as your organization grows. The tape backup system in which you've already invested money and time doesn't have to be thrown out when you decide to go to disk-based backups.

Since recovery from disk is almost always faster, it makes sense to have yesterday's or last week's backups on disk to be easily restored across the network. However, if you want to keep backup archives for months or even years, and for off-site storage of backups, tape may be the most effective (and least expensive) way to go.

So go ahead and buy that tape system for your small to medium sized network, and when you're ready for a high-end disk-based solution, you can move it into a new role for creating low cost archives.

About Deb Shinder

Debra Littlejohn Shinder, MCSE, MVP is a technology consultant, trainer, and writer who has authored a number of books on computer operating systems, networking, and security. Deb is a tech editor, developmental editor, and contributor to over 20 add...

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