Originating Author: David Floyer

Disk vendors have touted the death of tape; tape vendors have pointed out how green tape is. The bottom line of the SaskEnergy story is that a combination of both provides an optimum cost solution that meets SaskEnergy’s specific business needs.

The archiving retention edict from SaskEnergy senior management was that all data had to be retained for five years. The data warehousing solution was considered as separate from the archiving and restore solution. Data created as part of the data warehousing became data that had to be archived and restored if necessary.

The interesting aspect of the SaskEnergy solution is the balance between an immediate restore capability with an initial backup direct to disk, and the use of Spectra Logic tape libraries for longer term restoration and archiving. The main backup strategy was “incremental forever” using IBM’s TSM. The case for a hybrid disk/tape solution is compelling as the five year cost for disk-only is $4.6M as compared to $1.4M for the hybrid approach. Notably, the disk only solutions consumes about 8X the power. Specific features of TSM were used to manage Lotus Notes restoration and archiving, and to create monthly images of remote servers to facilitate remote restores. The overall strategy balances a good low cost solution for archiving against longer and more complex recovery restore times. To date, SaskEnergy has only had to test the recovery procedures, and has never had to use it in earnest.

The table and chart below show that the cost of a disk only solution is over four times higher than a mixed disk and tape library solution. The overall business case could change if:

• The probability of having to recover from older data was higher,
• The business benefit of quicker recovery from data in the tape library was more significant,
• There was a significant business benefit in being able to access the archived data (over and above the data warehouse data held).

Also shown in the table are the facilities costs. The facilities cost of disk are about eight times higher, going from ~$50K with tape to over $400K with disk only. The use of advanced MAID features such as AutoMAID from Nexsan might reduce that to about $200K over 4 years, but that is still four time higher than tape.

Action Item: The bottom line is there will continue to be a storage hierarchy, with a place for different technologies at each level. Working constructively together with all the technologies available will be more fruitful than second guessing the market.

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