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relationship between throughput and latency - 10GB

Posted on 2014-11-01
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Last Modified: 2014-11-17
Hi

I like analogy of a truck has high throughput (can cary allot) but likely high latency (slow).

My question is: If i replaced "all" of my NIcs and switches from 1gb to 10GB would I achieve "both" higher throughput "and" lower latency - lets say there is some distance latency of 1km - would 10GB cards/switchs see a faster response time buy putting more data on the wire per unit of time?

does 10gb improve throughput and latency
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Question by:philb19
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by:Thomas Wheeler
ID: 40417904
It's the type of nic you want to look at. If you are looking at copper than the throughput will increase put you will still have a higher letancy than if you were using fiber.
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Predrag earned 500 total points
ID: 40417905
Sure you will have better throughput, and probably you will have better latency, but maybe you will have no gain at all of your investment. The only gain will be on host that have SSD's or HDD's with raid configuration 0, 5, 10 (reading from that hosts) etc and on uplinks.
Why is that?
Wel, currently max HDD drive write speed is around 80MB/s, if transfer need to be written on local HDD theoretical limit for Gb network is 125MB. In my home Gb network I got max transfer speed at HDD write speed (ONLY with large files, with a lot of small files it is still so sloooooow). That is practical limitation of network speed, how fast data on HDD can be written (or read if data don't have to be written on HDD - but how much RAM you need for this if it is not written on HDD to have any use of great network speed?). So you can end up in situation where you spent huge investment and gain nothing. Of course in some environments you can have big network speed improvements (on places where usual is congestion - like uplinks, distribution and core switches) , but you need to know parts of network where you will really get improvements (probably won't have any improvements on access level switches if hosts are equipped with HDD).

Article that made me think about subject few years ago, and do testing of my own Gb network.
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by:David Johnson, CD, MVP
ID: 40417944
For throughput you have to consider everything in the chain  from source to destination (slowest one wins) . What 10G will give you considering everything else remains the same is the ability to handle more traffic through the pipe without network contention issues.  AKA going from a 1 lane highway to a 10 lane highway, great if you own a Ferrari but not so great if you own a Model T, getting on and off of the network pipe will be faster.  Latency should decrease as there is less contention for the pipe.
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by:BMarden
ID: 40418340
Latency is a function of media type and distance, if the new cards are using same media type over same distance latency would be constant.

This is true providing pipe is not saturated using current cards.  If the pipe is saturated then a bigger pipe will improve both though-put and latency.

BM
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by:Don Johnston
ID: 40418654
Latency is a function of processing.   On a fiber link, a bit will travel at the speed of... Light.  This is true whether it's 1g or 10g.  So the latency of a 1g link is the same as a 10g link.  If the NIC or intermediate device is saturated or is simply incapable of processing the incoming data, you're going to see an increase of latency regardless of the speed of the link.

This is an area where using the term "speed" can really create confusion.

And with respect to your analogy, I prefer the multi-lane highway analogy.  All the lanes have the same "speed" but because there are more lanes, you can move more cars (data).
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