Core Double-Take Availability requirements

Each Double-Take Availability server must meet minimum core requirements. If you are protecting certain workloads, your servers may need to meet additional requirements.

Operating system—There are different Double-Take Availability editions depending on the operating system you are using. Be sure you have the correct Double-Take Availability edition for your operating system.

Foundation Edition

Standard Edition

Advanced Edition

Premium Edition

Virtual Guest 5-Pack Edition

Virtual Host Standard Edition

Virtual Host Advanced Edition

Virtual Host Premium Edition

Microsoft Server Core 2008 R2 is supported for files and folders jobs. See the specific requirements for the workload type you are protecting for additional Server Core requirements. Server Core 2008 is not supported.

Each of the Windows 2003 operating systems require Service Pack 1 or later.

If you are protecting a domain controller or are using Windows Small Business Server, you should use full-server protection.

File system—Double-Take Availability supports the same file system format that Microsoft supports: FAT, FAT32, and NTFS.

System memory—The minimum system memory on each server should be 1 GB. The recommended amount for each server is 2 GB

Disk space—The amount of disk space required for the Double-Take Availability program files is approximately 70 MB. You will need to verify that you have additional disk space for Double-Take Availability queuing, logging, and so on. Additionally, on a target server, you need sufficient disk space to store the replicated data from all connected sources, allowing additional space for growth.

The program files can be installed to any volume while the Microsoft Windows Installer files are automatically installed to the operating system boot volume.

Server name—Double-Take Availability includes Unicode file system support, but your server name must still be in ASCII format. If you have the need to use a server's fully-qualified domain name, your server cannot start with a numeric character because that will be interpreted as an IP address.

Protocols and networking—Your servers must meet the following protocol and networking requirements.

Your servers must have TCP/IP with static IP addressing.
By default, Double-Take Availability is configured for IPv6 and IPv4 environments, but the Double-Take service will automatically check the server at service startup and modify the appropriate setting if the server is only configured for IPv4. If you later add IPv6, you will need to manually modify the DefaultProtocol server setting. See the Scripting Guide for details on modify that server setting.
IPv6 is only supported for Windows 2008 servers.
If you are using IPv6 on your servers, your clients must be run from an IPv6 capable machine.
In order to properly resolve IPv6 addresses to a hostname, a reverse lookup entry should be made in DNS.

Windows firewall—If you have Windows firewall enabled on your servers, there are two requirements for the Windows firewall configuration.

The Double-Take Availability installation program will automatically attempt to configure ports 6320 and 6325 for Double-Take Availability. If you cancel this step, you will have to configure the ports manually.
If you are using the Double-Take Console to push installations out to your servers (including pushing installations during protection of ESX virtual servers running Windows to an ESX host) you will have to open firewall ports for WMI (Windows Management Instrumentation) which uses RPC (Remote Procedure Call). By default, RPC will use ports at random above 1024, and these ports must be open on your firewall. RPC ports can be configured to a specific range by specific registry changes and a reboot. See the Microsoft Knowledge Base article 154596 for instructions. As an alternative, you can disable the Windows firewall temporarily until the installation is complete.

Windows Management Instrumentation (WMI)—Double-Take Availability is dependent on the WMI service. If you do not use this service in your environment, contact technical support.

Snapshots—Double-Take Availability uses the Microsoft Volume Shadow Copy service for snapshot capabilities. To use this functionality, your servers must meet the following requirements.

Snapshot operating system—Your servers must be running, at a minimum, Windows 2003 Service Pack 1. You should upgrade to Service Pack 2 or later so that several Microsoft patches that address memory leaks in the Volume Shadow Copy service are applied. If you do not have Service Pack 2 installed, you will need to review the patches available on the Microsoft web site and install those that correct the Volume Shadow Copy service memory leaks.
Snapshot file system—Your servers must be using the NTFS file system. If you are using a FAT file system, the FAT volumes will not be included in the snapshot set, and when the snapshots are reverted, the FAT volume will not be time-consistent with the NTFS volumes.
Snapshot data—Snapshots are taken at the volume level. For example, if your job is protecting D:\data and E:\files, the snapshot will contain all of the data on both the D: and E: volumes. If your job is only protecting D:\data (E:\files exists but is not included in the job), the snapshot will only contain the D: volume.
Snapshot configuration—If you have related data on different drives on your source (for example, an Exchange database on one drive and related log files on another), snapshots of each drive must be taken simultaneously so that the snapshots for each drive represent the same point in time. However, based on snapshot technology, different snapshots cannot be taken at the same time. To work around this limitation and guarantee data integrity on the target, you need to create a mount point, thus ensuring that one point-in-time consistent snapshot will be taken of both volumes at once. To create a mount point, create an empty folder on one of the drives. Using the Disk Management tool in the Windows Computer Management applet, remove the drive letter from the other drive. Then create a mount point by selecting Mount in the following empty NTFS folder and specifying the folder you just created. If you have multiple drives, create an empty folder on the drive for each of the other drives and create mount points to each of the folders. When the snapshot is taken of the drive, each mount point will be included in the snapshot. You will need to modify your applications to specify the new location for the files that are now on the mount point. For additional details on creating and using mount points, see your Windows reference manual. For details on modifying your applications, see your application reference manual.
Snapshot limitations—Sometimes taking a snapshot may not be possible. For example, there may not be enough disk space to create and store the snapshot, or maybe the target is too low on memory. If a snapshot fails, an Event message and a Double-Take Availability log message are both created and logged. There are also limitations imposed by Microsoft Volume Shadow Copy that impact Double-Take Availability snapshots. For example, for some operating system versions Double-Take Availability maintains only 64 snapshots because Volume Shadow Copy only maintains 64 snapshots. If 64 snapshots exist and another one is taken, the oldest snapshot is deleted to make room for the new one. Other operating system versions may maintain up to 512 snapshots. Another example is that Double-Take Availability snapshots must be created within one minute because Volume Shadow Copy snapshots must be created within one minute. If it takes longer than one minute to create the snapshot, the snapshot will be considered a failure. Additionally, Volume Shadow Copy will not revert snapshots of a volume with operating system files, therefore Double-Take Availability is also unable to revert a volume with operating system files. You must also keep in mind that if you are using extended functionality provided by Volume Shadow Copy, you need to be aware of the impacts that functionality may have on Double-Take Availability. For example, if you change the location where the shadow copies are stored and an error occurs, it may appear to be a Double-Take Availability error when it is in fact a Volume Shadow Copy error. Be sure and review any events created by the VolSnap driver and check your Volume Shadow Copy documentation for details.