Users shift to disk-based backup

Posted on October 01, 2004

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An end-user survey underlines the trend toward disk-to-disk backup and the reasons why.

By Thomas M. Coughlin and Farid Neema

This article is the first in a series that explores topics in backup and archiving, business continuance, and disaster recovery. Our analysis is based on an extensive (more than 200 questions per respondent) survey of 110 North American IT managers. The survey participants met the criteria of having backup and/or archiving responsibilities for IT operations that store a minimum of 500GB of raw disk storage. An earlier survey that covers similar topics was conducted in 2003.

Ten industries were primarily targeted: finance/banking, health, manufacturing, retail distribution, government, education, consulting, transportation, media/entertainment, and telecommunications. Sixty of the sites have more than 2 petabytes of disk capacity, with most of those sites in the transportation, entertainment, and telecommunication industries. The majority of the respondents in the education and consulting industries have less than 5TB of disk capacity.

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The full backup-and-archive report includes 171 figures that summarize site, industry, and revenue characteristics of the surveyed companies, as well as information on disk and tape backup/archive trends and end-user perceptions. (For more information on the full report, visit www.tomcoughlin.com, Technical Papers section. A companion report based on the survey is also available covering business continuance and disaster recovery. Highlights about tape backup trends to appear in the November issue of InfoStor.)

The trend is well underway

While tape is still used for virtually all backup applications, disk-based backup (secondary disk) shows the strongest growth potential. In fact, 62% of the survey respondents are already using some form of disk-based backup, and that number is expected to increase to 76% over the next 12 months (see figure, above). With the increased utilization of disk for backup, there is a growing interest in backing up in file format.

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It is interesting to note that the majority of disk-based backup applications currently use SCSI or Fibre Channel disk drives rather than ATA or Serial ATA (SATA) drives. Backing up to disk is not new and was not initiated with the new generation of ATA drives. Although it might seem surprising that SCSI and -Fibre Channel drives are more widely used for backup than ATA/SATA drives, it's important to note that higher-reliability ATA drives were introduced relatively recently, and a large number of managers are still skeptical about using ATA drives for secondary disk storage due primarily to reservations about reliability and/or performance (see figure, above). However, based on the survey responses we expect that over time most of those concerns will fade away, thus opening a greater opportunity for ATA/SATA in backup and other secondary storage applications.

Why disk-based backup?

Reliability of the backup process is of great concern to a large majority of the survey respondents. Close to half of the respondents report that more than 5% of their backups fail, which translates into unsuccessful restores. The respondents ranked reliability and integrity at the top of their backup concerns. Reliability problems are attributed in part to tape media, drives, and libraries, and disk-based storage is expected to improve reliability as well as performance (see figure, below).

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Second to reliability, performance issues related to backup speed and restore time are major issues for end users. The overall advantages in restore speed and backup window will increase the use of disk-based storage systems in backup applications.

A key factor to understanding backup needs is the recovery point objective (RPO), or the maximum time-window of data loss a business can afford for its most-critical applications. Our survey found that the population that cannot afford to lose more than three hours of input has increased by 30% compared to last year's survey. The use of snapshots (stored on disks) contributes to more efficient and more frequent backups.

The decreasing cost of disk-based storage options makes them more attractive for applications such as backup that have traditionally been the province of tape systems, And the survey results support projections for significant growth in disk-based backup.

Thomas M. Coughlin is president of Coughlin Associates, a consulting firm that specializes in data storage components, systems, and software. He is active in several industry organizations, including IDEMA, IEEE, SNIA, and BladeS. Coughlin is the organizer, with Farid Neema, of the Network Storage Conference, as well as organizer of the Storage Visions conference. For more information, go to www.tomcoughlin.com. Farid Neema is president of Peripheral Concepts Inc., which he founded in 1991. He is also chairman of the Network Storage Conference.


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