Online backup services for small and medium-sized businesses (SMBs) have been around for the better part of 10 years. Such services are part of the online storage services sector which false started with the dot-com boom and is now in its “second wave”. Some online backup providers survived the dot-com bust, but many did not and others emerged to replace those that failed or were acquired by ISPs and storage hardware vendors. Newcomers continue to enter the marketplace touting ultra-simplicity and low cost.
What has caused the latest resurgence in the online backup service industry? The answer is found in the convergence of three key components of the delivery of these services;
- Proliferation of affordable broadband Internet services.
- Continued decrease in the cost-per-gigabyte of disk storage.
- Exploitation of technologies such as Volume Shadow Copy Service (VSS) and “delta-block” incremental backups.
Proliferation of broadband
Like all computer based solutions, a program or service can only be as fast as its slowest component. Internet connection speed, and the amount and volatility of data to be backed up, are major factors in determining the viability of an online backup solution. Until recently the limiting component in any online service was the user’s connection to the Internet. That’s beginning to change.
In a January 2008 report from the National Telecommunications and Information Administration (NTIA) entitled “Networked Nation: Broadband in America 2007” (1) the NTIA reported that;
- According to the FCC’s data, at the end of 2006, broadband service was available in 99 percent of the nation’s ZIP codes, encompassing 99% of the nation’s population.
- Between 2001 and 2007 the total number of broadband lines in the United States has grown by more than 1,100 percent from almost 6.8 million lines in December 2000, to 82.5 million in December 2006, according to the most recent FCC data.
- By December 2006, 91.5 percent of ZIP codes had three or more competing service providers and more than 50 percent of the nation’s ZIP codes had six or more competitors.
- With increased competition and rapid technological change, broadband speeds continue to increase and prices continue to fall.
Decreasing cost of disk storage devices
A significant departure from tape based backups, online backup services are disk-based. This enables higher levels of redundancy, faster backup and restore times, and little or no intervention on the part of the user or service provider. Obviously large amounts of disk storage are at the core of online backup services. So as the cost-per-gigabyte of the underlying storage decreases, so also does the cost-per-gigabyte of the backup service decrease.
IBM’s Journal of Research and Development recently published the article, “Storage-class memory: The next storage system technology” (2) which noted:
- Disk drive capacity…will now double in 24–36 months. The reduction in the initial price of a new drive…will likely remain at 3–5% compound annual growth rate (CAGR).
- The 2007 high volume price estimates are $1.00–2.00/GB for enterprise disks and $0.30–0.60/GB for consumer disks.
- The recent trend, which is expected to continue indefinitely, is for the cost per gigabyte to decline at approximately 40% per year (CAGR).
Volume Shadow Copy Service
The Volume Shadow Copy Service (VSS) was introduced in Windows XP and Windows Server 2003. VSS allows volume backups to be performed while applications on a system continue to write to the volumes.
The VSS framework facilitates communication between applications, storage subsystems, and storage management applications (including backup applications). This framework enables you to define, persist and exploit point-in-time copies of storage data.(3)
VSS is designed to address common backup problems such as file inaccessibility, inconsistent file states, and the need to minimize service interruptions. It accomplishes this by capturing the state of a disk at one instant in time—a shadow copy of the volume. This volume copy exists side by side with the live volume, and contains copies of all files on disk effectively saved and available as a separate device.
Delta Block Backup
Minimizing the amount of data to be backed up and sent across the Internet for online backups is crucial to the efficiency of these services Traditional tape backup solutions utilize a combination of a full backup and subsequent incremental backups to capture data over time. Full backups simply copy everything from the source device to the tape. During incremental backups, files are examined and only new files or those which have been changed get backed up.
This incremental backup process is further improved using delta block processing. The delta block process evaluates changed data by breaking each file down into discrete blocks of information that are anywhere from 4 to 32K in size. Backup software can then utilize a cyclical redundancy check (CRC) mechanism to compare each block of the modified file with the corresponding block that has already been backed up. When the software detects a difference in the block, it will back up those blocks that have changed instead of backing up the entire file. (4)
Conclusion
Over the last couple of years the expansion of broadband Internet services, the declining cost of disk storage hardware, and the more effective use of software capabilities have breathed new life into this on-again-off-again segment of the storage market. There is no reason to think that these trends won’t continue.
The introduction and growth of fiber optic services, ever increasing disk drive bit density, and more wide-spread use of block-level and bit-level backup techniques will ensure that online backup services remain a viable, reliable, cost effective means of protecting business against data loss.
(1) “Networked Nation: Broadband in America, 2007”. National Telecommunications and Information Administration. January 2008. http://www.ntia.doc.gov/reports/2008/NetworkedNationBroadbandinAmerica2007.pdf
(2) Freitas, Richard F. and Winfried W. Wilcke. “Storage-class memory: the next storage system technology”. IBM Journal of Research and Development, Volume 52, 2008. http://www.research.ibm.com/journal/rd/524/freitas.pdf
(3) “Volume Shadow Copy Service Overview”. Microsoft Corporation. June 2008. http://msdn.microsoft.com/en-us/library/aa384649(VS.85).aspx
(4) Cougias, Dorian J., E.L. Heiberger, and Karsten Koop. The Backup Book: Disaster Recovery from Desktop to Datacenter. Lacanto, Florida. Schaser-Vartan Books, 2003.