By Henry Baltazar  |  Posted 2006-06-05 Print this article Print

With the addition of Double-Take Application Manager, the Double-Take continuous data protection platform gains the ability to manage application failover, complementing its core replication capabilities.

With e-mail taking on mission-critical proportions at many businesses, the blending of WAN-based replication with Microsoft Exchange failover management is timely and important. In eWeek Labs tests, Double-Take Softwares DTAM did a good job of automating the process of setting up Exchange servers in a high-availability scenario.

Click here to read a review of the Kashya KBX5000 data protection appliance.
DTAM is available free of charge to Double-Take customers. Double-Take for Windows is offered in three different versions: the $2,495 Server Edition, $4,295 Advanced Edition and $39,995 Datacenter Edition.

After installing Double-Take 4.4 on our source and target Exchange servers, we installed DTAM software on a management server in the Exchange Active Directory domain. DTAM quickly located our two Exchange servers, and, with just a couple of clicks, we established replication between the pair.

Exchange services on the source server were detected by DTAM, and we could decide which services we wanted to move over to the target server should the primary server become disabled.

DTAM does not require that the source server and the target server have identical hardware to function. However, we recommend that IT managers use similar hardware when setting up replication pairs to ensure that there isnt a dramatic drop in performance after a failover.

During tests, DTAM did a fairly good job of establishing our mail stores on the new target server, automatically setting up the destinations for the databases and log files on the target.

Double-Take has added best-practice knowledge to DTAM, allowing the utility to find configuration problems before establishing replication. For example, DTAM warned us that our primary Exchange server had circular logging enabled. Circular logging is a process that automatically overwrites older log files that have already been written to the Exchange database and is usually not recommended in mission-critical environments.

After initiating a failover operation, DTAM worked in conjunction with the Active Directory Domain Controller in our network to update DNS (Domain Name System) entries, which redirected Exchange requests to the new target server.

DTAM also simplifies failback operations, bringing services back to the primary Exchange server. During the failback operation, new data created on the backup server while the primary server is incapacitated is replicated back to the primary server.

Step It Up

DTAM is interesting and useful, but Double-Take Software needs to quickly ramp up the utilitys application support to remain competitive with products like XOsofts Assured Recovery, which supports Microsoft SQL Server and Oracle databases in addition to Exchange. Double-Take officials said support for Microsoft SQL Server will be added in the near future.

The Double-Take 4.4 management tools have not changed much since past releases. Using the tools, it was easy for us to create replication pairs to keep file shares on two sides of a WAN synchronized for data protection.

Double-Take 4.4 replicates on a byte level that minimizes the amount of data that needs to be sent over the WAN to keep replicas synchronized with primary servers.

Like previous editions, Double-Take 4.4 maintains ACLs (access control lists), ensuring that data is still protected even after it is replicated to another site.

Next page: Evaluation Shortlist: Related Products.


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