Rsync Always Copy from Scratch with Mounted NAS: Fixing the Issue

Are you having trouble with the rsync command always copying files from scratch when you are using a Network Attached Storage (NAS) device? This issue can be frustrating, especially if you are working with large files or have a slow network connection. In this article, we will explain the cause of this issue and provide a solution to fix it.

What Causes Rsync to Copy Files from Scratch?

When you use the rsync command to copy files from one location to another, it will by default only copy the changes made to the files. This is because rsync uses a technique called delta encoding, which only transfers the differences between the source and destination files. This makes rsync an efficient tool for copying large files or directories over a network.

However, when you are copying files to a NAS device, rsync may not be able to detect the changes made to the files. This is because NAS devices often use a file system that is not compatible with rsync's delta encoding. As a result, rsync will assume that the files have changed and will copy them from scratch, even if they have not been modified.

How to Fix the Issue?

The solution to this issue is to use the --whole-file or -W option with the rsync command. This option tells rsync to copy the entire file, regardless of whether it has changed or not. This will prevent rsync from always copying files from scratch when you are using a NAS device.

Here is an example of how to use the --whole-file option with rsync:

rsync -avW /path/to/source /path/to/destination

In this example, the -a option is used to preserve the file attributes, such as the ownership and permissions. The -v option is used to enable verbose output, which will show the progress of the file transfer. The -W option is used to copy the entire file, regardless of whether it has changed or not.

Additional Tips

Here are some additional tips to help you use rsync with a NAS device:

• Use a wired network connection instead of a wireless one. This will provide a faster and more reliable connection to the NAS device.

• Use a dedicated network for the NAS device. This will prevent other network traffic from interfering with the file transfer.

• Use a fast and reliable NAS device. This will ensure that the file transfer is completed quickly and without errors.

• Use the --delete option with rsync. This option will delete files on the destination that do not exist on the source. This will keep the source and destination in sync.

• Use the --compress option with rsync. This option will compress the files before they are transferred, which can reduce the amount of data that needs to be transferred over the network.

• Use the --exclude option with rsync. This option will exclude certain files or directories from the file transfer. This can reduce the amount of data that needs to be transferred over the network.

In this article, we have explained why rsync always copies files from scratch when you are using a NAS device. We have also provided a solution to fix this issue and some additional tips for using rsync with a NAS device. By using the --whole-file option with rsync, you can prevent it from always copying files from scratch and ensure that the file transfer is completed efficiently and without errors.

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