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I have the following setup:

  • A Synology DiskStation DS418 on which I used Seagate Skyhawk hard disks and then Kingston UV500 SSDs.
  • An ASUS ROG Rapture GT-AX11000 wireless router with support for Link Aggregation, and a 2.5 Gbps Ethernet port.
  • A desktop PC with an ASUS XG-C100C network card, connected to the router, on the 2.5 Gbps Ethernet port. The network card is capable of 10 Gbps Ethernet connections, and it works well on 2.5 Gbps too.

I enabled Link Aggregation on the NAS and transferred data between the NAS and the desktop PC, and then compared transfer speeds, with the Link Aggregation enabled and with it disabled. I ended up with the following results:

When using the Kingston SSDs:

enter image description here

when using the Seagate HDDs:

enter image description here

I did not expect my transfer speeds to double, but the speed gain seems too small - 1% or less. It's just too little.

Can you share with me why Link Aggregation does not help in improving the transfer speed in a significant manner?

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IEEE 802.3ad Link Aggregation without LACP balances the load across your bundle by applying one of several link choosing algorithms. The problem is most of these use the MAC address of the source and destination machine. These MAC algorithms are usually the default ones, if a choice is even available. Since your MACs cannot change, then the same link is always used and you only get one link of bandwidth. If you can change your link choosing algorithm, you might get more performance.

802.3ad makes more sense when you have one server serving several devices, or you are connecting two networks of many devices together (a backbone link). If you use another laptop to start transferring files, then you will notice a total increase in throughput.

If you have a setting to enable Link Aggregation Control Protocol (LACP) on both your device and your router/switch, you should enable that. This fixes all the issues noted above as both devices treat the bundle as one link. This option might not be available on your router/switch; It is an enterprise feature. I am surprised ASUS supports Link Aggregation at all.

| improve this answer | |
  • I added a note about LACP. Check if it is supported on your router. – Andy Feb 19 '19 at 23:27
  • I enabled Link Aggregation on the router too, not just the NAS. The results above are with LA enabled on both devices. – Corporate Geek Mar 5 '19 at 17:45

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