Q: What type of system requirements do I need to configure Double-Take? Do I need identical hardware and software for the secondary backup server?A: Because Double-Take is a software-based replication system, it does not require identical hardware or dedicated server links. Working with another disk or server located on a LAN or WAN, Double-Take only requires that the secondary server(s) have adequate disk capacity to hold the data being replicated from the primary server. Q: Can I setup Double-Take to replicate to multiple servers and vice-versa? Does Double-Take support WAN based backups?A: Yes. Double-Take can be configured within a single server system, or between multiple servers: many-to-one, one-to-many and daisy-chain. These methods offer departments and organizations with a wide range of flexibility to employ backups. For example, small departmental networks with limited server resources can use the single-server configuration to add data and system fault tolerance within a single server. Additionally, large enterprise systems can use Double Take's many-to-one and one-to-many modes to centralize backups to one server or distribute data from one central server to multiple disks and servers connected to a LAN and/or WAN. Q: What is the difference between mirroring/duplexing and Double-Take? Can I implement both configurations?A: Disk mirroring or duplexing includes one server with two identical hard disks; each disk is a mirror image of the other. In this situation, the actual mirroring occurs on a block or track basis, - at the disk level. As a result, only whole partitions can be mirrored or duplexed. Mirroring usually requires more data to be transmitted as every change may require an entire disk block to be re-mirrored. With Double-Take, files, directories, and server volumes can be replicated. Double-Take supports replication between different versions of Windows NT. For example, data can be replicated from a Windows NT 4.0 to Windows 2000. Finally, Double-Take does not require identical hardware. Q: If my primary server fails, can users login to the backup server?A: Yes. If the primary server fails, users can easily login to the secondary server and continue operations with minimal downtime and data loss. Q: Does Double-Take support failover? And if so, does replication continue during failover?A: Yes. The failover module runs on the target server, and continuously monitors the source servers. Whenever a source server fails, the failover module tells the target server to pick up the failed server’s name, shares and IP address. It also runs a failover script, allowing you to automatically restart key applications. Double-Take can handle multiple failovers at the same time. During failover, the other production servers continue to replicate their data to the target, even while it’s operating in failover mode.
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