Questions About Ethernet Port Link Aggregation

Video streaming isn't really that demanding over gigabit ethernet.  Even 4K 3-D video won't exceed 100 megabits, and that is only 10% of your gigabit bandwidth.  And most 4K is much less. 

FullHD BluRay won't exceed ~54 megabits (5% of your gigabit bandwidth). 

Most video downloads use much lower bitrates (FullHD mkv files are often around 8-10 megabits).

So for your specific use case, you probably don't need Link Aggregation.

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XrayDoc88 wrote:

...Linking two ethernet ports will not double the speed...

 

That depends on the details. If the device accessing the NAS is also using link aggregation, there are some bonding modes that would double the speed.

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XrayDoc88 wrote:

2. Since the bandwidth from the ReadNAS to the switch would be doubled, wouldn't this help with the data flow from the NAS when streaming to two separate computers on the same LAN?  I'm thinking of the situation where two people are watching two different movies on two different smart TVs or on two different computers.

 

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It can help in this case.  It is not guaranteed to improve the performance, but it shouldn't hurt performance.

If you are using LACP, then the system chooses a specific NIC for each data flow.  That's what the hash mode does.  If you only have two computers accessing the NAS, there is a 50-50 chance they will end up using the same NIC.  When that happens, the performance is the same as not using aggregation.

If you choose a static LAG on the Cisco device, then you'd want to choose the "round-robin" mode in the NAS.  The NAS will then alternate the packets (packet 1 goes on NIC-1, packet 2 goes on NIC-2, ...)  That can double the speed (if the receiver is also bonded using a static LAG). 

But if the receiver isn't bonded, then it can result in lost packets (because the NAS is delivering packets faster than gigabit ethernet can carry them).  In this case, It's best to enable ethernet flow control on the receivers (and if you have smart switches, on the switches too).

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XrayDoc88 wrote:

3. Since the aggregated link would only be between the ReadyNAS and the switch, should I choose a "static" LAG?

 

 

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I'd suggest LACP, as that avoids the possibility of the packet loss/queue overflow issue I mentioned above.  If you were using aggregation in the NAS clients as well, then I'd consider using a static LAG. 

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XrayDoc88 wrote:

 

4. There were lots of other choices for the type of Link Aggregation on the ReadyNAS, including some "hashes" I believe.  Which choices would you recommend, or do those choices only apply for dynamic LAGS with LACP enabled?

 

 

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For static LAG, just use round-robin. 

For LACP, either layer 2 or layer 2+3 are reasonable.  In practice it doesn't matter much. 

Also, the hash mode is only about selecting the NIC for transmission of each packet.  The switch won't know what hash the NAS is using, and it often will use a different one.  The Netgear switches I use don't allow me to configure the hash on the switch (and I believe they use layer 2).