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DoubleTake and XOsoft Comparison
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Date published: March 9, 2010
DoubleTake and XOsoft Comparison
Presenting two continuous data protection technologies for your high availability needs.
A company’s data has always been important. But just having a backup of your data from Noon, 3PM, 6PM or even an hour ago isn’t enough anymore. Data needs to be available in real time because even small periods of downtime can bring productivity to a halt and lead to serious bottom-line consequences.
A critical question that may follow, for IT professionals at a mid-sized company, “is our data backup approach effective for my organization?” And, as with most software solutions, there are approaches that give the impression they are a complete, viable solution–but turn out not being the right solution for your company.
Take for example, RAID (redundant array of independent disks), which gives you protection against a single hard drive failure. However, this data tape backup, won't protect you against a natural disaster or catastrophic hardware failure. It offers some security, but can be costly, cumbersome and system resource heavy. It also only offers a snap shot, with the potential to lose a whole day's data in the event of a major loss.
Now, take into consideration, Continuous Data Protection or CDP, which brings near or pure real-time data protection within reach of mid-sized businesses. CDP solutions track data modifications and store the changes securely at a remote site. Because this data exchange is continuous, in the event of data loss on the primary servers, information can be recovered almost seamlessly from the backup servers. Pure CDP allows recovery to pick up the data stream at any given point in time, where near CDP uses snap shots, like tape back-ups, but with much shorter intervals, and no need to load the tapes manually.
With Gartner Group research suggesting that major data loss sounds a death knell for 90 percent of businesses who suffer one, within five years, the question is not so much can you afford to implement CDP, as can you afford not too? DoubleTake and XOsoft offer CDP solutions you might consider as an IT professional in a mid sized company. Here we evaluate the differences and similarities between the two.
DoubleTake and XOsoft Similarities:
Both DoubleTake and XOsoft offer continuous data replication at byte level across asynchronous connections. This, combined with their data compression capabilities and storage hardware independence, means multiple guest server data (the information on the servers you want to protect) can be stored on a single host, or destination, server. This can make them cheaper to deploy for data storage, one argument to use in defending their costs. Frustratingly, though, if you want to use them as hotsites to provide continuity in the event of primary site downtime, you will still need to deploy them on a one to one basis.
Both solutions offer the ability to exclude files or folders from replication which saves the bandwidth necessary for replicating non critical files. In addition, they offer open file and encrypted file replication, which means work in progress, at the point of data loss, can be recovered.
Both offer Failover and automatic Failback functions with multiple notification options through email, GUI, event log and SNMP, which are designed to reduce downtime and ease data deployment between systems in the event of data loss.
The option to use Command Line support or management consoles on either system offers the flexibility to either let the real wizards in behind the scenes for complete control or allow non tech-savvy users to recover data quickly.
The systems do however have different strengths and weaknesses, which you should take into account when considering which might be most appropriate for your need.
DoubleTake:
DoubleTake allows multiple levels of data compression, giving you more control over the bandwidth and storage needed to replicate data. It also offers application integration with “inband” commands, giving IT staff the ability to monitor integrity of data on the backup server. Integration of Pre and Post Failover Scripts allows custom actions to be performed before and after a data switch. However, there is no support for registry replication.
DoubleTake also requires different licenses depending on which operating system you are using on the guest machine. The host server can be running on a different operating system. You need to take care when choosing a license, and be aware that some licenses offer replication services only, and not full server Failover.
In particular, unless you use Full-Server Failover, the Small Business Server Edition offers a replication only license. If you are using Storage Server Edition, there are two possible licenses. The SSE license offers Failover functionality, where the SSE Replication license does not. If you are running and Itanium based system, you should be aware that the Itanium Edition does not support Full-Server Failover.
It is also worth noting that although the DoubleTake for Windows can be upgraded to “True CDP” for additional cost, the standard solution is “near CDP.” It does, however, offer scheduling per replication set, so you can, to some extent, determine how much data is “at risk” between set.
XOsoft High Availability:
XOsoft High Availability, on the other hand, does support registry replication, although. doesn't offer multiple levels of data compression, just a simple “On/Off” option. There is no scheduling of replication sets, because XOsoft is “pure CDC” and so there is no scheduling to be done. It also “maintains functional backups of complete database and application servers."
There's also no support for custom pre and post Failover scripts. Instead XOsoft focuses on ease of usability, with wizards for creating new data recovery scenarios, automated remote installation, and the CDP Repository which allows end users to recover data without burdening IT staff.
XOsoft works on Microsoft Exchange, MS SQL Server, MS IIS Web servers, Oracle, file servers and applications on 32- and 64-bit Windows operating systems, AIX, Linux and Solaris servers, with support offerings tailored to your servers.
Although remote storage probably makes more sense in terms of disaster recovery, the host servers can be housed on the same LAN, or connected across a WAN. Additionally, XOsoft supports Virtual IP sharing between guest and host machines, removing the need to change IP addresses in the event of a Failover, and it can be configured to work with Informix, making it familiar for anyone used to dealing with data backup.
SSD drives are still expensive compared to conventional hard disks, but at the rate of price declines, this new storage option will soon see more than a 100 percent compound annual growth rate and will become strategic in various IT areas. They will include consumer devices, corporate data storage, entertainment equipment, and other embedded IT systems.
Comparing DoubleTake and XOsoft:
www.itcomparison.com offers commentary on a comparison between DoubleTake and XOsoft in which DoubleTake appears to outperform XOsoft. According to this report:
• During initial synchronization with compression disabled, DoubleTake performed fifteen percent faster than XOsoft.
• With compression enabled, DoubleTake performed “twice as fast.”
• During resynchronization with compression disabled DoubleTake took five percent longer.• With compression enabled, Double Take was thirty percent faster.
• During a Failover, DoubleTake required only two thirds of the time it took XOsoft to complete a Failover.
• The Exchange performance on XOsoft is described as “a bit slower than with DoubleTake.
However, on investigation it is clear the data for this comparison is drawn from the Lionbridge.com competitive analysis testing report, commissioned by DoubleTake. The IT Comparison Team comments that “DoubleTake provides better flexibility when it comes to compression levels,” which, while it is a valid point, raises the question about what level of compression was used during the testing, as this is not specified.
That being said, none of these issues surfaced during comparison testing by real world testing of both systems on “two test cycles per product, one each with Exchange 2000 running on Windows 2000 Advanced Server and one running with Exchange 2003 on Windows 2003 Enterprise Server."
Based on this testing, Network World had this to say: “WANSync HA Exchange earns our Clear Choice designation because it adapted quickly to our setup, presented clear Exchange installation-specific options, and required no subsequent intervention to complete the processes of Failover detection, Failover and \bringing our hotsite/back-up site online."
Another issue raised by ITComparison was that of licensing. Where DoubleTake licensing is based on the operating system, XOsoft is application based. ITComparison sees this as a matter of flexibility, suggesting, “you can move your license across the several servers you want to protect freely as needed as licenses are not tied to the application it protect ."
On the other hand, Network World reports, “In our two-forest, two-Exchange server example in which we simulated a headquarters and a manufacturing branch topology, four licenses of DoubleTake were required, but only two licenses of Exchange server were required.
Conclusion:
From this analysis it might seem that XOsoft would be an obvious choice. Indeed, if Exchange Server is your main concern, it probably is the best way to go. In Network World's tests, it was the only solution that didn't lose any outbound messages during the Failover/Failback maneuvers.
On the other hand, if file and print sharing are a higher priority for you, or if you rely heavily on NTFS and you encrypt a lot of files, you should consider the potential for file sharing and encryption issues. In this case the platform independent DoubleTake might be a better solution. In either case, careful consideration of your licensing needs for each solution is imperative if you are to deploy the most cost effective solution.
Suggested reading:
http://www.itcomparison.com/DR/XOsoftvsDoubleTake/XOsoftvsDoubleTake.htm
http://www.networkworld.com/reviews/2004/0503rev.html
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Productive Corporation is a specialized software reseller that helps small and medium businesses across North America with software initiatives in security, storage and infrastructure. We provide subject matter expertise, access to technical support, and relevant content for IT staffs in the Mid-Market.
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