Disk is becoming increasingly popular as a long-term storage medium for data that is being retained in increasing volumes. The main reason for this is that retrieval times from disk are much faster than from media such as tape or optical discs. However, the power consumed by disk is much greater than that required by tape or optical devices, which are not switched on all of the time, unlike disk-based storage devices.
The power consumption for tape compared with disk has been put at as little as 2%, using metrics such as the fact that tapes are generally removed from a tape library and taken off-site unlike disk, which remains available often 24/7. One of the problems of using tape as an archiving medium is that retrieval times are slower, particularly if the tape is stored off-site. It can be more difficult to locate the required data, as it often has to be restored to disk before a search can be performed, and if a discovery request has been received for specific information the timeframe to locate and present it could be as little as a few hours. While this is achievable for disk, if the data has been properly managed, it is not possible with tape.
Another option is to use optical media, which is offering much larger storage capacities than in the past, and again, uses much less power than disk. According to research by Plasmon, its ultra density optical (UDO) devices are up to 17 times more energy efficient than equivalent magnetic disk systems over a 10-year period. While optical media can be searched much faster than tape, a downside is that to be WORM-compliant, optical media is often not re-writable, and if an organization has to destroy individual records, the company will have to retain multiple disks containing a few records each. Therefore, the administrator or records manager has to be highly organized to ensure that individual disks are filled with records that will be deleted at the same time.
Organizations need to consider whether they can continue to store their entire archive on magnetic disk-based systems when they are attempting to show their green credentials in other areas. However, they must also ensure that data is discoverable within the timeframe laid down by the particular regulations or legislation, or that is demanded by a court.
In the long-term, organizations need to consider other media such as tape or optical that consume less power than disk and require less space. However, vendors must also continue to develop these alternatives to make them more comparable with disk in terms of discoverability and reusability. Only then will organizations feel confident enough to replace disk-based archives. For the moment, the best that organizations can achieve is to retain data that needs to be retrieved quickly on disk, and archive other data that does not need to be discovered so quickly on a greener media.
Source: OpinionWire by Butler Group (www.butlergroup.com)
