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NAS, Gigabit, TCP window size

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argint

Occasional Visitor
Hi All,

This could be a very stupid question...but...

When looking to achieve max transfer speeds to a NAS, can the TCP window size of the *sending* computer have any effect on transfer rate? ie can transfer rate be improved?

Regards
Argint
 
I have never played with any of the TCP/IP parameters.
What are you getting for speed and what is the setup?
 
Hi All,

This could be a very stupid question...but...

When looking to achieve max transfer speeds to a NAS, can the TCP window size of the *sending* computer have any effect on transfer rate? ie can transfer rate be improved?

Regards
Argint

Generally in my experience if you are using Windows you should not need to mess with window sizes to see high performance on a local LAN. They are are automatically adjusted by default. I believe that most of the later Linux Kernels also auto adjust window sizes so they shouldn't cause any problems for max TCP performance. Just remember that we are only talking about max network performance and not what the rest of the computer components are capable of. What I mean is your network components might be capable of sending/receiving data at 119 MB/sec but that does not mean your hard drives can actually read/write data that fast. For example your hard drives might only be able to read/write at 60 MB/sec so your actual transfer speeds would most likely be limited to around 55 MB/sec. Hope that didn't confuse you.

The short answer would be yes it can but only if the window size is not set correctly to begin with. From what I can tell most of the more current OSes auto tune window size so in small LAN environments the default settings can usually provide good performance. If possible use a tool like Iperf or Jperf to test TCP performance and see if there are any network bottlenecks.

Does that help or did I confuse you more?

00Roush
 
Hi all. Many thanks for the replies. I do love this site!!!

It was really just an inquiry, Id been reading an article on getting higher gigabit speeds beteen servers, and they started in to adjusting the parameters I mentioned.

My setup is a buffalo link station pro duo, and I know they are not the fastest. With a procurve gigabit switch i got about 120 Mbs if i recall correctly.

Jumbo frames sizes made no difference to the transfer rate, but id read here that its not given theat frame size will affect transfer rates.

anyways thanks for the really informative replies.
cheers
argint
 

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