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Home > Disk-to-disk vendors respond to user backup demands |
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Goodwin found that other disk-to-disk products offered various levels of ease and functionality, noting that EMC's Clariion Disk Library (CDL) product offers a very good blend between ease-of-use and functionality. "It's not the easiest to use and it's not the most functional, but when you put all those things together, it [EMC] is a very well-balanced, well-presented product." Goodwin found the CDL so good overall that it was only one of three disk-to-disk products to receive the Diogenes Shortlist Candidate recommendation, along with the Storage Consolidation Platform (SCP) from Gresham Computing PLC and the Axiom by Avamar.
The Fujitsu-Siemens CentricStor virtual tape system clearly ranked at the bottom of Goodwin's list achieving fair scores in all but recoverability where it earned a very good rating. "Bottom line is that even with professional services help, we could not a get a single Windows server configuration to the point of doing a backup," Goodwin says. "They've got a million excuses, but CentricStor is a very complicated product." Selecting the right product Disk-to-disk product selection can be a challenge because of the proliferation of disk systems available -- each often specializing on a particular storage objective. For example, you probably would not select a VTL disk system for long-term archiving. The shift from tape to disk-to-disk or disk-to-disk-to-tape can also be disruptive to the environment, changing hardware as well as software tools. Analysts suggest the following points that can help you identify the best product for your own production environment. Consider cost, capacity and management overhead. Disk-to-disk products can be pricey, so be sure to evaluate the acquisition and maintenance costs for any prospective purchase. Select capacities that can retain data for an adequate amount of time. For example, an organization seeking to retain four weeks worth of backups on disk before offloading to tape (as a third tier of storage) should carefully evaluate the amount of disk space needed to meet that objective today -- and confirm that the system is sufficiently scalable into the future. Investigate the management tools that support the disk-to-disk product to determine its ease-of-use and compatibility with other hardware in your environment. Evaluate the amount of disruption you can tolerate. Consider the impact of a new disk system on your current backup strategy and determine how much change will be required to accommodate the new technology. For example, organizations that need to minimize changes to their existing backup process may opt for a VTL, while companies that are more tolerant of change can leverage other disk-to-disk products. "If you're OK with making some changes to the backup environment, and enjoy even greater speeds and efficiencies, then by all means look at non-VTL solutions like Avamar or Data Domain," Taneja says [see the SearchStorage.com article on Backup strategies here]. Consider the importance of data compression. Disk systems can still be more expensive than tape systems, so it's important to optimize the use of available disk space and get the most mileage from disk upgrades. Data deduplication, also called commonality factoring, intelligent compression or capacity-optimized storage, is an emerging technology that saves space by eliminating redundant blocks of file data. Consider the upgrade path. Many disk-to-disk platforms create fixed storage volumes -- this is particularly apparent in VTL systems where disk volumes are often created to match tape sizes. Unfortunately, resizing established disk volumes can be extremely disruptive, forcing administrators to unload, reformat, reinitialize and reload the data on each resized volume. Conversely, creating unnecessarily large media volumes up front can waste valuable storage space. Understand the process involved in resizing storage volumes once they're created. Consider the remaining feature set. Beyond compression, look for other features that will benefit your environment. For example, corporations managing sensitive or personal data may prefer a disk-to-disk product with encryption to maintain security. Other products may also support a variety of disk types simultaneously, allowing for multiple tiers or storage service levels within the same system. Best practices for implementation Disk-to-disk products are widely available from a multitude of manufacturers, so there is no single set of best practices in every possible scenario. In most cases, the storage vendor can provide the best practices and configuration options that are most appropriate for their particular products. However, analysts offer some general policies that can help you get the most from any disk-to-disk tool. Don't abandon tape until disk is proven. The introduction of a secondary disk storage system does not signal the end of tape storage. In virtually all cases, existing tape systems are relegated to a third tier of storage (D2D2T) where disk can provide fast backups and restorations, but tape continues to serve as long-term archival or off-site storage. This preserves the current investment in tape infrastructure. "Don't give up on tape immediately," Taneja says. "Maintain your love and hate relationship with tape a little while longer." Eventually, tape backups can become less frequent -- and eventually be phased out if desired. Leverage disk for more restore points. The speed and capacity available with disk storage often allows for additional backup/restore points. While this will inevitably use more disk space, it also reduces the potential for data loss between an event and the most recent backup. Suppose a backup is only made every 24 hours. A fault can potentially wipe out up to 24 hours of work. If you make a backup every six hours, more disk space is needed, but there is considerably less potential for loss. Snapshot technology is an ideal disk-to-disk tool for aggressive restore points [see the SearchStorage.com article on Snapshot tools here]. Include everyday disk management with new storage. Disk storage requires regular maintenance, including disk defragmentation, provisioning, volume sizing and other high-level tasks. "The disk management is a crucial piece that you have to add to your regimen," Taneja says. "However you manage disks today, you must apply those practices to the secondary [disk] storage." When a secondary disk tier is added to the storage infrastructure, additional disk maintenance will also be required to support the new storage, so be sure to include the new disk system in any regular maintenance or management schedules. Work toward evolving storage objectives. Analysts point out that new storage platforms offer new opportunities for efficient, cost-effective utilization of media. Employing new disk storage platforms using a tired old tape backup paradigm is often a waste of the potential that technology offers. Revise existing backup strategies to reap the greatest benefits from your new disk storage platform. For example, regular full backups to disk may not be very efficient -- incremental backups may make far better use of disk space. ***
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