LAG working at half speed

mickypen
mickypen Posts: 17  Freshman Member
10 Comments

I have been trying to set up link aggregation between my PC and NAS via my Zyxel XGS1250-12.

My PC has an Asus 10G network card conntected to one of the 10G ports on my switch. My NAS - A Terramaster T5-221 has two 1Gb ports which are connected to ports 5 and 6 on the switch. I have created a bond on the NAS between the two ethernet ports and it shows on the NAS portal as 2000Mb/s.

On the switch, I went to Link Aggregation and checked the "LAG 2 - Port 5 and 6" checkbox and clicked apply.

So from this, I would expect that I would be able to copy a file up to the NAS from my PC at more than 1Gb/s - but it doesn't.

On the switch System page, it shows only a tiny amount of packet usage on port 6.

Can anyone help me find out what I am doing wrong please?

Best Answers

  • Zyxel_Nami
    Zyxel_Nami Posts: 474  Zyxel Employee
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    Answer ✓

    Hello @mickypen

    Your concern regarding achieving half speed with LAG should be explained by its inherent behavior. When a single user sends data to the NAS, the switch directs this single traffic flow through one physical port, capping the speed at 1Gbps. This is a standard behavior for link aggregation, where individual traffic flows don't exceed the bandwidth of one link.

    The real advantage of LAG comes into play when multiple users (such as PCs) are interacting with the NAS. Each user can potentially use a different link, allowing for better overall utilization of the aggregated bandwidth.

    Additionally, the redundancy feature of LAG ensures that your NAS remains accessible even if one link goes down, providing greater network resilience.

    Zyxel Nami

  • mickypen
    mickypen Posts: 17  Freshman Member
    10 Comments
    edited January 15 Answer ✓

    Thank you all for your explanations

  • RSaull
    RSaull Posts: 24  Freshman Member
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    edited January 19 Answer ✓

    @mickypen

    It's important to understand that while the bandwidth of a 2-port LAG link is 2Gbps, an individual flow will max out at 1Gbps. It's a highway with a 100MPH speed limit. We can add another lane and 2 cars can go 100MPH, but a single car can never go 200MPH. We're increasing the amount of traffic that can be carried, but not the max speed.

    EDIT: I picked up this analogy from PatrickFarrell on SpiceWorks a while back. Great conversation in that thread about LAG and LACP btw.

All Replies

  • PeterUK
    PeterUK Posts: 2,702  Guru Member
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    edited January 13

    Yes the way LAG works is not ideal I don't know why it can't be made better.

    I LAG can have a hash type by MAC/IP Src/Dest (even port which helps a bit if supported) so from the NAS it can only send to say 192.168.0.2 at 1Gb down one link if you have another PC with 192.168.0.3 it will send 1Gb down the other link. Same problem when going from switch to NAS

  • mickypen
    mickypen Posts: 17  Freshman Member
    10 Comments

    Hi PeterUK, thanks for getting back to me.

    I am sorry though, I don't understand your answer.

  • PeterUK
    PeterUK Posts: 2,702  Guru Member
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    edited January 13

    Have two PC's upload a big file to your NAS ideally one odd IP one even like 192.168.0.2 and 192.168.0.3 given the XGS1250-12 is MAC SA & DA LAG hash it be by odd and even MAC of the PC's

  • mickypen
    mickypen Posts: 17  Freshman Member
    10 Comments

    This has nothing to do with two PCs

    I am trying to set it up so that one PC can upload a single file to the NAS at 2Gb/s

  • PeterUK
    PeterUK Posts: 2,702  Guru Member
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    You can't LAG don't work that way for one PC

  • Zyxel_Nami
    Zyxel_Nami Posts: 474  Zyxel Employee
    First Anniversary 10 Comments Friend Collector First Answer
    Answer ✓

    Hello @mickypen

    Your concern regarding achieving half speed with LAG should be explained by its inherent behavior. When a single user sends data to the NAS, the switch directs this single traffic flow through one physical port, capping the speed at 1Gbps. This is a standard behavior for link aggregation, where individual traffic flows don't exceed the bandwidth of one link.

    The real advantage of LAG comes into play when multiple users (such as PCs) are interacting with the NAS. Each user can potentially use a different link, allowing for better overall utilization of the aggregated bandwidth.

    Additionally, the redundancy feature of LAG ensures that your NAS remains accessible even if one link goes down, providing greater network resilience.

    Zyxel Nami

  • mickypen
    mickypen Posts: 17  Freshman Member
    10 Comments
    edited January 15 Answer ✓

    Thank you all for your explanations

  • RSaull
    RSaull Posts: 24  Freshman Member
    First Anniversary 10 Comments Friend Collector First Answer
    edited January 19 Answer ✓

    @mickypen

    It's important to understand that while the bandwidth of a 2-port LAG link is 2Gbps, an individual flow will max out at 1Gbps. It's a highway with a 100MPH speed limit. We can add another lane and 2 cars can go 100MPH, but a single car can never go 200MPH. We're increasing the amount of traffic that can be carried, but not the max speed.

    EDIT: I picked up this analogy from PatrickFarrell on SpiceWorks a while back. Great conversation in that thread about LAG and LACP btw.