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General source and target server requirements

Operating system—There are different licenses depending on the operating system you are using. Be sure you have the correct license for your operating system. Each of the Windows 2003 operating systems listed in the chart require Service Pack 1 or later.

License	Windows 2003 and 2003 R2 Operating Systems	Windows 2008 and 2008 R2 Operating Systems 1	Virtual Servers
License	Windows 2003 and 2003 R2 Operating Systems	Windows 2008 and 2008 R2 Operating Systems 1	Guest-Level Protection 2	Host-Level Protection 3
Foundation Edition 4	Storage Server Edition Small Business Server	Storage Server Edition i386 and x64 Small Business Server Standard and Premium x64 Foundation Server with SAK Essential Business Server x64	N/A	N/A
Standard Edition	Storage Server Edition Small Business Server Web Edition i386 and x64 Standard Edition i386 or x64	Storage Server Edition i386 and x64 Small Business Server Standard and Premium x64 Foundation Server Essential Business Server x64 Web Server i386 and x64 Standard Edition i386 and x64	1	N/A
Advanced Edition	Storage Server Edition Small Business Server Web Edition i386 and x64 Standard Edition i386 and x64 Enterprise Edition i386 and x64	Storage Server Edition i386 and x64 Small Business Server Standard and Premium x64 Foundation Server Essential Business Server x64 Web Server i386 and x64 Standard Edition i386 and x64 Enterprise Edition i386 and x64	1	N/A
Premium Edition	Storage Server Edition Small Business Server Web Edition i386 and x64 Standard Edition i386 and x64 Enterprise Edition i386 and x64 Enterprise Itanium IA64 Datacenter i386, x64, and IA64	Storage Server Edition i386 and x64 Small Business Server Standard and Premium x64 Foundation Server Essential Business Server x64 Web Server i386 and x64 Standard Edition i386 and x64 Enterprise Edition i386 and x64 Itanium Edition Datacenter Edition i386 and x64	Unlimited	N/A
Virtual Guest 5-Pack	Any valid Foundation, Standard, Advanced, or Premium Edition operating system		5	N/A
Virtual Host Standard Edition	N/A	Standard	N/A	ESX hosts-5 Hyper-V hosts-Unlimited
Virtual Host Advanced Edition	N/A	Standard Enterprise	N/A	ESX hosts-10 Hyper-V hosts-Unlimited
Virtual Host Premium Edition	N/A	Standard Enterprise Datacenter	N/A	ESX hosts-Unlimited Hyper-V hosts-Unlimited

Note:

Microsoft Server Core is supported for data workloads. See the specific requirements for the workload type you are protecting for additional Server Core requirements.

File system—Double-Take Availability supports the same file system format that Microsoft supports: FAT, FAT32, and NTFS.
System Memory—There are different memory requirements depending on the operating system you are using. Be sure you have at least the minimum amount of memory for your environment. You may want to consider having at least the recommended amount of system memory.

Operating System	Minimum System Memory	Recommended System Memory
Any Windows i386 operating system	128 MB	At least 512 MB
Any Windows x64 operating system	512 MB	At least 1024 MB

Disk Usage—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.

Note:

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.
Microsoft .NET—Double-Take Availability requires the Microsoft .NET Framework version 3.5 Service Pack 1. You can install this version from the Double-Take Availability CD, via a web connection during the Double-Take Availability installation, or from a copy you have obtained manually from the Microsoft web site.
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.
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 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.
Windows Firewall—The installation program will automatically attempt to configure ports 6320, 6325, 6330, and 6332 for Double-Take Availability. If you cancel this step, you will have to configure the ports manually.

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 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.