Are disks taking over?

Dr Carl Windsor, chief technical consultant of TeleCity, discusses the disk versus tape debate.

The disk versus tape storage debate is much like arguing the benefits of owning a top of the range 4x4 car versus a standard family saloon.

Both cars have a valid purpose, most of us would prefer the 4x4, but the saloon is more practical and cost effective and gets the job done well. However, this doesn’t stop the majority of 4x4's being used to drop the kids off at school.

Claiming disk storage to be the future of the backup industry is similarly misguided at this point in time.

Recent developments in disk storage technology have allowed snapshots of changes to be taken at very frequent intervals. This makes disk storage an ideal solution for short-term data backup in situations where the critical factor is the frequency of backups.

Where disk-based backup falls down is on long-term storage. For example, what would happen if you were to attempt to restore a corrupted data set, only to find that it had been corrupt for some time and all of your disk snapshots were also corrupt? 

On tape, you would have the option of rolling back to copies taken days, weeks or even years ago.

Proponents of disk backup technology would argue that this issue could be overcome by addition of extra disks to the storage array but at $15–20 per MB compared with $0.001 per MB for tape media - according to IDC - the cost of incrementing disk storage capacity could quickly become higher than the value of the data it is protecting. 

With the introduction of new regulations such as the Freedom of Information Act and Sarbanes-Oxley (although a US regulation, it will affect US companies based in the UK), the requirement for long-term storage is set to increase significantly for the foreseeable future. For this reason, we can reasonably predict that the future for low-cost, long-term tape media is a good one.

Disaster recovery is a common driver in backup requirements and having all of your data in one location is not a good solution to this problem.

Disk replication technology has improved significantly over the last few years but an additional cost for a secondary site and replica disk array and fibre to connect the two will always make offsite tape vaulting a more viable solution.

With a recent survey by Infostor stating that 71 per cent of respondents were planning to purchase tape storage and 64 per cent planning to purchase disk-based solutions this year, it appears that the consumers have come to the same conclusion.

There is room for both 4x4's and reliable saloons in the storage town. With 3.5 per cent of the respondents in the InfoStor survey looking to outsource their backup to a third party storage provider, there are organizations well placed to deliver a cost-effective solution tailored to the customers requirement and not driven by the technology or physical location.

TeleCity is a leading European provider of colocation and data centre services.

www.telecity.com

in a nutshell

  • Claiming disk storage to be the future of the backup industry is misguided. 
  • Disk storage is an ideal solution for short-term data backup in situations where the critical factor is the frequency of backups
  • On tape, you have the option of rolling back to copies taken days, weeks or even years ago. 
  • With the introduction of new regulations the requirement for long-term storage is set to increase significantly for the foreseeable future.

September 2005

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