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List:       gentoo-user
Subject:    Re: [gentoo-user] Network throughput from main Gentoo rig to NAS box.
From:       Frank Steinmetzger <Warp_7 () gmx ! de>
Date:       2023-09-24 17:04:34
Message-ID: ZRBsItNNIT9BNJa1 () kern
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Am Sat, Sep 23, 2023 at 05:54:21PM +0200 schrieb ralfconn:

> On 9/23/23 14:04, Dale wrote:
> > Howdy,
> > 
> > As most everyone knows, I redone my NAS box.   Before I had Truenas on it
> > but switched to Ubuntu server thingy called Jimmy.   Kinda like the
> > name.   lol   Anyway, Ubuntu has the same odd transfer pattern as the
> > Truenas box had.   I'm not sure if the problem is on the Gentoo end or
> > the Ubuntu end or something else.   I'm attaching a picture of Gkrellm so
> > you can see what I'm talking about.   It transfers a bit, then seems to
> > stop for some reason, then start up again and this repeats over and
> > over.   I'm expecting more of a consistent throughput instead of all the
> > idle time.   The final throughput is only around 29.32MB/s according to
> > info from rsync.   If it was not stopping all the time and passing data
> > through all the time, I think that would improve.   Might even double.
> > 
> > ...
> > Has anyone ever seen something like this and know why it is idle for so
> > much of the time?   Anyone know if this can be fixed so that it is more
> > consistent, and hopefully faster?
> > 
> I found a similar pattern when I checked some time ago, while transferring
> big (several Gb) files from one desktop to the other. I concluded the cause
> of the gaps was the destination PC's SATA spinning disk that needed to empty
> its cache before accepting more data. In theory the network is 1Gb/s
> (measured with iperf, it is really close to that) and the SATA is 6Gb/s so
> it should not be the limit, but I have strong doubts as how this speed is
> measured by the manufacturer.

Please be aware there is a difference between Gb and GB: one is gigabit, the 
other gigabyte. 1 Gb/s is theoretically 125 MB/s, and after deducting 
network overhead you get around 117 MB/s net bandwidth. Modern 3.5″ HDDs 
read more than 200 MB/s in their fastest areas, 2.5″ not so much. In their 
slowest region, that can go down to 50..70 MB/s.

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