From a traffic perspective, the characteristics of network backup are:
- Backup operations are scheduled to take a snapshot of the contents of a host machine, such as a desktop or server.
- When the scheduled time is reached, backup operations begin. This generally consumes as much of the host's CPU and disk resources needed to complete the operation. It also consumes as much network bandwidth as is available on the link between the target host and the backup host.
Conventional backups can become problematic when they consume more network bandwidth than can be spared for normal operations. That's when continuous backup systems become very attractive. Most well-known backup software providers and many other companies offer backup tools that monitor file system activity and take snapshots as updates occur. Rather than waiting for a time window to open to copy everything (full or complete backup) since the last backup, these systems capture everything that has changed and spread the processing and bandwidth necessary to avoid overloading systems and networks. How do you know if your company is a candidate for continuous backup? Here are some questions to ask:
- Do you need a new backup solution?
If so, it may make sense to choose continuous backup to avoid possible congestion or resource consumption issues.
- Do your current backups involve sufficient data volumes so that normal off-hours time windows aren't long enough for your backups to complete?
If so, continuous backup probably represents your best hope of capturing and maintaining backups of key systems and servers.
- Do your operations span multiple shifts or require 24/7 operations?
The obvious case is 24/7, but the same thing occurs when multiple shifts don't leave enough off-hours time to complete full or incremental backups. Continuous backup is a good option for capturing and maintaining backups. (Note: this advice assumes it's impractical for you to install a storage area network or additional, separate networking capacity to handle backup.)
- Must certain servers, such as e-mail, database, e-commerce, or transaction processing, remain available 24/7?
Even if your work schedule otherwise permits conventional backups, constant accessibility requirements for some servers may need continuous backup.
- Do business, regulatory or legal requirements mean that you cannot afford to lose data?
Backups capture only the data that's available to them when they occur. In environments where data or transaction losses have serious consequences or where liability is an issue, continuous backup offers the added assurance that no data, records, or transactions that occurred prior to the downtime event will be lost. For conventional backup, all changes or additions that occur after the most recent backup would be lost.
Though continuous backup is more expensive than conventional backup, it does offer extra protection. Vendors such as Veritas Software Corp., EMC Corp., and Symantec Corp. offer products that provide continuous backup coverage. Lesser-known but capable offerings are also available from Softek Storage Solutions Corp., Availl Inc., Peer Software Inc. or Atempo Inc.
Ed Tittel is a regular contributor to numerous TechTarget Web sites, where he acts as a resident expert on networking, markup languages, IT certifications and career development. He's also the author of numerous books on subjects that range from home theater PCs to TCP/IP protocols and services.