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Straight Talk: Backup to tape

Missed out on the previous part of our new Straight Talk series? Check out the introduction to data backup and deduplication.

In the first section, we provided a brief introduction about how the movement from using tape for backup to using disk with deduplication is well underway within more and more IT organisations. However, many factors should be considered when making the move to disk, since it is not as straightforward as simply buying some disk. That is why it is necessary to understand the needs of your backup environment and know the key questions to ask of your vendor in order to avoid the 10 most common pitfalls listed in the final instalment.

In this section, we will explore the deficiencies of tape and how backing up to disk can help address these problems.

For as long as most IT professionals can remember, backup has been accomplished by having a backup application copy data every night from all primary storage on the network to tape. The organisations still backing up primarily to tape keep tapes onsite for local restores and store tapes offsite in case of a site disaster.

Most organisations keep multiple weeks to years of backups, due to the need to go back to certain points in time and do any of the following:

  • Restore from a failure or corruption
  • Restore deleted or overwritten files
  • Recover data for legal discovery
  • Recover data for external audits or recover historical files to meet other user and business requirements

As a result, the amount of backup data can be 30 to as much as 100 times or more the size of the primary storage.

Example: If the primary storage is 20TB and you keep 10 weeks of retention onsite and three years of monthlies offsite, then you are keeping 46 copies of the primary storage in backup storage. This would require almost 1PB of backup storage (1PB of backup storage to keep retention for 20TB of primary storage).

The massive amount of data in backup storage driven by the number of copies kept, meant that tape was the only cost-effective solution. Since tape per gigabyte is far less expensive than disk, backup was always written to tape for cost reasons.

However, although tape media is inexpensive, it has many deficiencies:

  • Backups fail for a host of reasons
  • Restores fail because of failed backups, corrupted tapes, missing files, blank tapes, and other problems
  • IT staff spends excessive time managing manual backup processes
  • Security is poor, as data is leaving the building when tapes are transported offsite - even onsite, tapes may not be in a secure area
  • Wear and tear - as tapes are reused, they wear or stretch, increasing the chance of failed backups and subsequent restores
  • Tape libraries are more prone to breakage compared to other hardware in the data centre, because they have many moving parts

To address the problems of tape, the solution is clearly backup to disk. If the cost of straight disk per gigabyte was the same as tape, everyone would use disk for backup for the following reasons:

  • Backups complete successfully, since writing to disk is reliable
  • Restores work, since the data is reliably backed up to disk, and therefore the restore is also reliable
  • Manual movement and handling of tapes is avoided, as disk drives remain in data centre racks
  • Security issues are negated, since disk sits in the data centre rack behind physical lock and key and within network security
  • Disk is not damaged by heat or humidity, since disk is in a hermetically sealed case in the temperature and humidity-controlled data centre
  • Uptime is greater because spinning disks fail far less often than tape drives and robotics

The benefits of disk are clear. The goal is to use disk for backup — and the way to do it is to have the required disk approximate the cost of tape, including libraries, drives, media and offsite storage.

This guide explains the various backup complexities, enabling you to ask the right questions and make the right decision for your specific environment and requirements. Stay tuned for the next part of this guide, which will be live on ITProPortal shortly.

Bill Andrews is the president and CEO of ExaGrid Systems.