Re: transfer speed data
On Wed 23 Dec 2020 at 16:47:21 (+0200), Andrei POPESCU wrote:
> On Mi, 23 dec 20, 10:56:36, Nicolas George wrote:
> > Andy Smith (12020-12-23):
> > > "gigabyte" is not a network speed. You probably mean gigabit
> >
> > No, gigabit is 10³ bits, there is no "per second" involved either.
> >
> > Anyway, why would anybody honest want to use this kind of unit to
> > measure an actual speed is beyond me. The only point to speak in
> > kilo/mega/gigabits per second instead is to make the numbers seem larger
> > to attract clueless customers. Moreover, the ratio between these numbers
> > and the actual useful network speed is not eight at one might believe,
> > because they measure below the low-level network protocols.
>
> I took that to mean the theoretical maximum.
Well, I took it to mean that mick crane had read the sides of the
boxes that the hardware came in, and mistranslated it into the OP.
So I would assume he's talking about 1000BASE-T cards.
Fortunately the engineers that design the electronics know better than
to try and stuff 1Gbps down the wires, particularly my old Cat5 ones,
and they manipulate the bits to reduce the symbol rate (think "baud")
to what the wire can manage.
> For a quick estimation of "good" transfer rates a ten to one ratio is
> probably sufficient, e.g.:
>
> 1 Gbit/s = 1000 Mbit/s ~ 100 M(ilion) bytes (octets) per second
>
> (which is approximately 95,367432 MiB/s according to 'qalc')
>
>
> If one reaches that in real world transfers (as opposed to specialized
> tests) any further significant improvements will likely require hardware
> upgrades.
Some sort of rough calculation between the expected/nominal bit rate
and the actual data rate achieved is certainly useful, if only to
ascertain whether the link itself is performing well. For that, you
need to reduce the amount of processing (like encryption) of the
data, and any other tasks tying up the CPU(s). Just for the test,
obviously.
If you're still getting poor transfer rates, you might want to swap
cables and (if you're dealing with several hardware systems) cards.
For example, on the cable front, a cable with damaged blue or brown
pairs will give perfect 100BASE-T performance but not 1000BASE-T,
which uses all eight wires. (For the same reason, structural wiring
using brown for the telephone sockets will have the same problem.)
Cheers,
David.
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