About Restore

There is an interesting blog discussion between Dipash Patel from CommVault and W. Curtis Preston from Backup Central and TruthinIT regarding the increasing or decreasing benefits of deduplication ratios. They take different perspectives on the benefits of increasing deduplication ratios and I will highlight their points and add an additional one to consider.

Patel argues that increasing deduplication ratios beyond 10:1 provides only a marginal benefit. He calculates that going from 10:1 to 20:1 results in only a 5% increase in capacity efficiency and suggests that this provides only a marginal benefit. He adds that vendors who suggest that a doubling in deduplication ratios will result in a doubling cost savings are using a “sleight of hand.” He makes an interesting point, but I disagree with his core statement that increasing deduplication ratios beyond 10:1 provides only marginal savings.

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HP recently announced the availability of LTO-5 and they are currently hosting industry luminaries at their HP Storage Day. I received a question on Twitter from John Obeto about LTO-5 and what it means to VTL and wanted to answer it here. Note that I previously blogged about LTO-5.

The challenge with data protection is ensuring that you meet your backup and recovery requirements, and most companies have fixed SLAs. The advent of LTO-5′s larger tape sizes is nice, but tape size is not the problem, the issue is real world performance. Quantum’s LTO-5 specification suggests maximum performance of 140 MB/sec which is an impressive statistic, but in practice few end users achieve this. The challenge is even greater when you think about minimum required transfer rates as discussed in my fallacy of faster tape post

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I was recently pondering TSM’s implementation of target deduplication and decided to review ESG’s Lab Validation report on IBM TSM 6.1. There is quite a bit of good information in the paper, and some really interesting data about TSM’s target deduplication.

Before discussing the results, it is important to understand the testing methodology. Enterprise Strategy Group clearly states that the article was based on “hands-on testing [in IBM's Tucson, AZ labs], audits of IBM test environments, and detailed discussions with IBM TSM experts.” (page 5) This means that IBM installed and configured the environment and allowed ESG to test the systems and review the results. Clearly, IBM engineers are experts in TSM and so you would assume that any systems provided would be optimally configured for performance and deduplication. The results experienced by ESG are likely the best case scenario since the average customer may not have the flexibility (or knowledge) to configure a similar system. This is not a problem, per se, but readers should keep this in mind.

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TSM presents unique deduplication challenges due to its progressive incremental backup strategy and architectural design. This contrasts with the traditional full/incremental model used by competing backup software vendors. The result is that TSM users will see smaller deduplication ratios than their counterparts using NetBackup, NetWorker or Data Protector. This post explores four key reasons why TSM is difficult to deduplicate.

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