Virtual Disk Libraries

Disk to Disk backup with disk libraries - the way to go

Data Growth
As data grows exponentially, it has become more costly and time-consuming for IT managers today to manage tape-based data backup systems due to the fact that it demands continuous monitoring, complex configuration, repeated tuning and constant supervision. Tape drives can be notorious for frequent failures, slow load and transfer rates, and sluggish seek times. This sort of performance can prove costly for any business but affects SMBs (Small to Medium Business) the most as they have less to play with.

In order to provide a solution to these types of problems, a virtual disk library (VDL) may be the solution, which brings the emulation functionality of tape libraries to the high-performance and highly reliability of disk arrays. A VDL gives disk storage the look and feel of a tape library including virtual drives, media slots and advanced media management features without the added cost usually associated with disk backup.

What is a Virtual Disk Library?
Operating like a real tape library, a disk library offers the same advantages of tape but with the added bonus of disks high speed and low cost. Customers can freely design any number of customised virtual tape libraries on disk, each with its own specific number of tape drives, tape slots and tape sizes to precisely fit their environment. Data can be backed up in multiple data streams over the LAN at the same time and these can then be retained on disk or migrated off to tape for archiving purposes. Yet, when restoring, customers do not have to re-stage data on tape first through their disk subsystem. They can restore directly from tape or from disk, depending on where the data is.

By storing backup data on a disk library, users can run data copy or duplication jobs off line, without impacting their networks, applications servers or workstations whilst being assured that there will be none of the mechanical penalties of tape backup over a network, such as shoe-shining, or a slow data stream host.

Using a disk library means users can capture their data, whether it's trickled, blasted or gently passed along and it'll end up at the receiving end of a virtual media slot as a save-set, thereby improving the backup window performance markedly. During the first phase of a staged backup job, all selected data can be backed up to the virtual library (disk). Once this process is complete, the second phase known as Data Copy can begin and copy the save-set from the virtual library to a physical tape. This two phase process can be automated and defined in the job. Once the data copy is complete, the space used in the disk library can be cleared and available for another backup.

No shoe-shining
There are two key reasons why users might want to use the disk library staging solution. The first scenario would be one where users are backing up a file system that contains millions of files where the server is not able to read the files quickly enough to stream to tape drives. This will result in shoe-shining which may lead to premature drive or media failures.

Overcome nonexistent backup windows
The second scenario would be one where the backup window is too small to backup several clients onto a limited number of tape drives. Users should, in this case, create a disk library with enough virtual drives to backup all clients simultaneously. This performance depends on the network bandwidth, and a gigabit network would almost certainly be a requirement.

Cost-effective solution
SMBs must, at all times, keep their business costs in mind. At the end of the day, a disk library is a flexible tool that helps decrease the backup window and, at the same time, increase ROI (return on investment) on tape libraries by streaming the tape drives at highest rate possible.

Virtual Disk Library Summary

The advantages in summary:
 Direct restore capability without re-staging to disk
 Backup scheduling, operation imitates real tape library
 Fully integrates with real tape library resource management
 Supports Full, Incremental, & Differential backups
 Complete control over: numbers of drives, slots, and tape media size
 Improved cost performance ratios when compared to tape alone