Offload Data Transfer (ODX)

Overview:

Offload Data Transfer (ODX) is a transparent fast file movement feature in Windows Server 2012 that enables ODX capable storage arrays to bypass the host computer and directly move data within or between compatible storage devices.

Key scenario of using ODX:

In a traditional host-based file transfer when a host needs to copy or move a file on a SAN, the windows OS reads the data in its buffer then transfers across the network to the destination server and then writes it back to the storage through the destination server.

If we compare this situation where you have a Hyper-v host having multi-terabyte VHDX files and you need to move these VHDX files from one disk to another, one cluster to another or from one storage array to another. Using the traditional host-based file transfer mechanism will take quite long to complete this task.

Using ODX feature in Windows Server 2012 you can bypass this long route and let the VHDX transferred directly within or between compatible-storage devices.

How ODX works:

ODX uses a token-based mechanism for reading and writing data within or between compatible-storage arrays. Instead of passing data across the network to the destination server it passes a token which represents the data. The token is then delivered to the storage array and then the actual data transfer takes place within or between the storage arrays internally.

ODX supports moving and copying using command line tools such as copy, xcopy, robocopy or even with drag & drop.

Fig: How ODX works

Benefit of using ODX:

• As ODX bypasses the host and transfers data directly within or between the storage devices it reduces the resource utilization on host such as CPU and memory.
• It enables SAN to move and copy files much faster.

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Limitations:

• Works with NTFS but not with ReFS and FAT.
• Doesn't support encryption, data deduplication and compression.
• Files less than 256 KB are transferred through traditional file transfer.
• Storage spaces and dynamic disks are not supported.

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