Link aggregation is something that's "nice to have" when it comes to a NAS, but it's something most people arguably don't need. It makes use of multiple LAN ports in order to increase bandwidth, bundling physical network ports into a virtual link called a Link Aggregation Group, or LAG. However, there are some reasons why it's worth setting up, from the practical to the educational.
6 Increased bandwidth
But not to the same client
This is the obvious one, and probably the first reason people think of when it comes to link aggregation. Essentially, you can combine the total bandwidth of your Ethernet ports. If you have two 1Gbps Ethernet ports, it doesn't quite mean you can have 2Gbps actively from one device to another, but you can have two separate data streams going out to different clients at 1Gbps each.
To saturate this bandwidth, you'll also need the necessary hardware to manage it. If you have two 5Gbps Ethernet ports, for example, a four-HDD RAID 0 setup will net you a read speed of approximately 2.2GB/s, or 17.6Gbps. Your HDDs can keep up with whatever your network may throw at them, but other RAID configurations and drive combinations might not be capable of matching the bandwidth required.
5 Redundancy
A backup if one port fails
When it comes to building mission-critical systems, redundancy can be incredibly important. In this case, having a second Ethernet port that can be switched to should the first fail can be useful, and most NAS devices will handle that changeover immediately once configured to do so.
In theory, your total bandwidth output will decrease in this case, but that's better than not having a connection at all. You can then try and diagnose what the problem is, and without losing total connection to your NAS in the meantime.
4 Load balancing
Intelligently split connections
If you do have a lot of traffic going into or out of your NAS, link aggregation will allow for you to split traffic across multiple ports. Rather than saturating one and then immediately moving to the other with any following traffic, your NAS can dynamically allocate traffic to each port so that neither is fully saturated.
Imagine your NAS has two 1Gbps ports, and you're downloading four files at 250Mbps each. Rather than having all four files go through the first interface, your NAS can split them so that two files are downloaded on the first interface, and two files are downloaded on the second. This makes it possible to still use the first interface, rather than all four files being downloaded through it.
3 Use your NAS to its full potential
You have the ports, use them
Many NAS devices come with multiple Ethernet ports, with premium models packing as many as four that can be actively used. These ports can be set up to work with a managed switch and form a LAG. It's not necessarily the case that it's useful for most people, but why not spend the time to figure out how to use them right if you have them?
As well, setting up a LAG gives you an excuse to try and find a way to make the most of them, which might lead to some interesting projects you can attempt to undertake. The ports are there, use them!
2 Improved multi-user access
Make your NAS better for friends and family
If your NAS is shared across multiple people, link aggregation can enable a better experience for them. Because connections are split dynamically over ports, there's not a risk of one person saturating it and harming the experience for others who might also be using it at the same time.
If you know there are multiple people who use your NAS and they might be using a lot of data in either direction, link aggregation can protect your other users from being affected by a potential network saturation. If you run a NAS that handles a lot of media streaming, for example, the benefits of link aggregation might actually be quite noticeable.
1 Learn about networking
It can be an educational experience
When it comes to link aggregation, there are typically one of three systems you can set up, though some NAS devices might have more (or less). These are:
- LACP
- Failover
- Load balance
LACP is the most common, and it allows your NAS to negotiate with the network switch to bundle ports together. LACP bundles multiple ports into a single logical link, but the downside is that it requires a network switch that understands and supports it. It will automatically handle failovers too, so that if one connection fails, it will use the other as the primary connection.
LACP is complex as it's highly recommended to use ports that are the exact same, and a mismatch in ports of different speeds might result in strange behavior. Traffic will typically be balanced across all of the ports, and it can reconfigure itself if a port suddenly fails. It's also not recommended to use with an iSCSI configuration.
Failover works exactly as it sounds, where it will simply just swap the connection over from a primary interface to a secondary or tertiary interface. Finally, load balance will balance outgoing traffic across the active ports based on protocol header information and can accept traffic on any port. There's a lot more that you can learn in-depth about networking when it comes to setting up link aggregation, and one of the biggest benefits of configuring it can be that learning process.
The process for configuring link aggregation will differ from NAS to NAS and device to device, but it's pretty easy to do on TrueNAS, with a lot of documentation available from the developers on how to implement it.