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I've got 2 NAS drives that are connected through a router via Ethernet.

If I have a wireless laptop and request a large amount of data to be copied from one NAS drive to the other, does the network traffic go direct from the one drive to the other, going via the wired network, or does the network traffic go via my laptop? That is, from the NAS drive's wired network, to the wireless network and then back to the wired network?

Is this a common cause of bottlenecks when copying a large amount of data? And if so, is there a way to avoid it?

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Can I assume you're copying from your laptop and not using any copy / paste tools built into the NAS drives? – Dave Nov 26 '12 at 10:28
That is correct. – Strontium_99 Nov 26 '12 at 10:31
up vote 3 down vote accepted

Connect your laptop to LAN, map NAS drives on your laptop and copy data using Total Commander – because it's much faster than Windows Explorer's copy speed.

Also, some NAS have a built-in FTP server and client. You can start the FTP server on one side and use it on the other side to copy the files between them, without using your laptop.

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Nice one. Thanks for the info. – Strontium_99 Nov 26 '12 at 10:40
If your NASs will let you run rsyncd/rsync (Linux) on them, you can copy data even faster directly between the two NASs - because rsync is usually setup to copy only the parts of files that have changed, not whole files. You can replace the firmware on some NASSs with freenas which will let you do such things and more. (Doing so will probably void any warranty on your NAS.) – Joe Nov 27 '12 at 8:26
Nice Answer Kaveh! – Arash Mar 19 '13 at 15:31
First part of the answer is wrong, the second part is true. – bokan Oct 3 '13 at 7:20
'Total commander is much faster than Windows Explorer copy speed' - Do you have any reference to verify that? I can find videos proving in some cases, one is faster than the other! – Dave Mar 25 '14 at 7:07

Depending on how you perform the copy of the data, if you are using your laptop and Windows Explorer to copy the data from one NAS to the next, perhaps copying the data from one network drive to another, then I believe the data copy does go through your laptop since that is the device working as the device in the middle. You could however perform a direct copy of the data from one NAS to the next. As another user mentioned most NAS devices can use FTP, however if you have the option to use RSYNC, then I would go with that method.

Many NAS devices have some version of Linux running in them and as such they probably can perform an RSYNC directly between the two, thus eliminating your laptop as the bottleneck and you might be able to do a block level backup which will only back the data in the file that has changed instead of the whole file, which will lessen the demands on the network.

Another thing you can do to improve the performance between the two NAS devices is to place both of them on the same switch and if you can Link aggregate the NICs on the NAS devices then that too will help, and better yet if you can have a dedicated switch for the NAS devices to connect to, then have the "NAS switch" connected to the LAN, it will also help reduce the additional traffic that would be on the network between the two NAS's

I hope this was helpful, good luck

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