It was just about five years ago that the industry first started talking in earnest about open-systems virtual tape libraries (VTLs). Data volumes had grown to the point where even the most sophisticated IT users were having difficulty meeting backup objectives with their existing tape-based environments, and frustrations with tape-based backup had reached an all-time high.

As the price of ATA/ SATA disks fell, the disk-based backup market opened up, and VTLs began to catch the attention of early adopters of disk-based backup primarily because of their simplicity.

Because a VTL emulates a physical tape library, organizations are able to implement it with minimal changes to their existing data-protection environments and processes. This means they can use their existing backup software, follow familiar backup processes, and leverage the (often-hefty) investments they have made in tape hardware while reaping all the benefits of disk-based backup: faster backup and recovery performance, easier management, improved disaster recovery, and lower CAPEX and OPEX tape costs.

Today, the underlying appeal of VTLs is still the same-simplicity-but the market has evolved significantly. Disk-based data protection (VTLs or otherwise) is still maturing, but there is no longer any question of its viability. More than 50% of the users we recently polled as part of an ESG Research project regarding VTLs said they used a combination of disk and tape for backup, and nearly one-quarter reported an all-disk backup infrastructure. And, of those respondents who backed up to disk, about one-third said they used VTLs (see “How pervasive is VTL adoption?” p. 27).

This article takes a look at the VTL market from an end-user perspective. Is the technology meeting users’ expectations? How is the technology being used, and what features/functionality do users say they want to see added to VTL solutions going forward? This information is extracted from a recent ESG Research Report, VTL adoption and market trends.

Is It Meeting User Expectations?

In general, end users are very happy with their VTL implementations. As evidence, ESG asked respondents 1) to rate their organizations’ overall satisfaction with their current VTL solutions and 2) to indicate the impact these solutions have had in their environments-more specifically, how they have affected backup performance, recovery performance, and media management. As shown in the figure, 27% of the respondents indicated they were “very satisfied,” and 63% said they were “satisfied” with their VTL implementations.

Although the above data is a good barometer of overall satisfaction with VTL, it doesn’t tell us anything specific about users’ experiences with VTL to date; specifically, has the technology helped them improve backup-and-recovery performance and reduce media management headaches? Some of the conclusions of our research include the following:

Backing up to VTLs instead of tape has significantly improved backup performance. More than half (54%) of respondents said they were able to exceed their existing backup objectives (i.e., complete backup jobs in allotted windows) by backing up to VTL systems instead of tape. An additional 38% said that they were now able to meet existing backup objectives as a result of backing up to VTLs. Only 2% said VTLs had “not improved their ability to back up data in allotted windows.”

VTLs have also made a marked difference in data-recovery performance. For example, 38% of the survey respondents said they were able to exceed recovery objectives (both recovery point and recovery time) by using VTLs, while 48% said they were now able to meet their recovery objectives. Only 6% reported no improvement in recovery performance by backing up to VTL versus tape.

ESG expects overall levels of backup-and-recovery performance to increase as users keep more secondary data online (on VTLs or on other types of disk-based backup devices) for longer periods of time, providing quick access to data in outage/recovery situations. As with most new technologies, VTL solutions are being phased in by users generally on an application- by-application basis, not necessarily starting with the more mission-critical data sets.

Also, while users are starting to keep backup data online for longer periods of time, we expect retention periods to lengthen over time as capacity- optimized protection (COP) technologies such as data de-duplication, compression, and delta differencing become more mainstream, making more-efficient use of disk capacity. Simply put: The more data that is online and the longer it is kept online, the faster the potential recovery performance.

Backing up to VTLs has had a significant impact on early adopters’ tape media management costs. For example, 33% of the survey respondents said the switch to VTLs has “lowered their tape media costs significantly,” and another 37% say the switch has “lowered their tape media costs somewhat.”

Keep in mind that this is with the majority of respondents still doing weekly full backups to tape. As tape’s role in these environments lessens, users can expect to reap even greater economic benefits from using VTLs and other disk-based backup platforms.

How Are VTLs Being Used?

The industry has witnessed a clear shift in end-user attitudes toward disk, particularly over the last six to twelve months. But have users’ backup habits really changed? Do backup schedules reflect a growing reliance on disk (in this case, VTLs)? Are users keeping data on disk longer?

To shed some light in these areas, ESG asked respondents (who have deployed VTLs) to describe their organizations’ current backup practices. At a high level, 85% of VTL users said they have already eliminated tape from their daily backup schedule, and 37% said they had all but eliminated it from their weekly process.

When we drilled down, we still found that more users were doing a combination of nightly incremental backups to VTLs and weekly full backups to tape than they were doing nightly and full backups to VTLs.

However, ESG expects the storage media balance to shift even more in favor of VTLs (and other disk-based technologies) over time as user confidence in and adoption of VTLs continue to increase. Again, we expect data de-duplication to play a key role here.

As for VTL retention periods (i.e., how long users are keeping backup data on VTLs), our research shows that the majority of early adopters keep backup data on VTLs for one month or less, although it isn’t uncommon for some organizations to use VTLs for longer-term storage.

ESG believes that as disk-based platforms, such as VTLs, continue to mature and data de-duplication and content search/indexing features become mainstream, data retention periods will increase. As they do, it will become increasingly important for users to build a continuum of data-protection technologies to ensure IT resources and dollars are being spent wisely and that recovery-driven SLAs are continually being met.

While “feature sets” are not currently driving VTL purchasing decisions today, ESG believes they will become critical factors in the near future.

Not surprisingly, data de-duplication and better/easier management topped respondents’ VTL “wish lists” (see figure). As data volumes increase, data de-duplication, as well as other storage optimization technologies such as data compression and delta differencing, will become increasingly popular because they enable users to significantly reduce the back-end capacity footprint.

As VTL implementations scale in size and scope, we also believe the need for better/easier management will increase. Users will need better ways to automate movement to/from VTL solutions, as well as quicker, more-efficient ways to recover data from these devices.

Therefore, although only 19% of early adopters selected search capabilities as a feature on their wish lists, we expect this percentage to increase going forward. As the size and scope of the VTL repositories increase (i.e., as VTLs become used as both backup and archive targets), the ability to easily search across contents will become paramount.

As for other features, such as better performance, recoverability, and disaster-recovery features, there were no surprises in our survey results. Overall, early adopters say they are satisfied with their existing VTL solutions but, again, as VTLs are used more broadly, they will need to become more-efficient.

As for security, another media “hot button,” although users do not seem overly concerned with the security of their VTL solutions (the majority of early adopters describe their VTL security features as “adequate”), ESG believes users should take all necessary steps to ensure the security of VTL-resident backup data.

This is true for data at-rest as well as data in-flight-in those cases where VTL systems at remote offices are transmitting data over the WAN to a centralized location, as well as in cases where data is being moved off a VTL and onto tape for long-term archival. If they haven’t done so already, users should evaluate and deploy the necessary access control, data encryption, and network encryption technologies to make sure these information assets are protected at each phase of the information life cycle.


As data volumes grow and regulatory, corporate governance and e-discovery requirements become more demanding, the ability to improve recovery performance will continue to rise to the top of the list for both large enterprises and small to medium-sized businesses (SMBs). ESG continues to see a decline in users’ recovery time objectives (RTOs) and recovery point objectives (RPOs), meaning that they are being asked to recover data faster and that their tolerance for data loss is shrinking.

Indeed, this shift toward a “recovery-centric” mindset-and its potential impact on the market for VTL solutions-is evident in the purchasing motivations of the next wave of VTL buyers. As this shift occurs, ESG expects vendors’ feature sets- including technologies such as data de-duplication, replication, encryption, and content search-to become increasingly important.