file transfers faster in parallel?

[MZ]

Weird observation...

When I'm transferring files to and from my 7.2 box, it goes faster when
I simultaneously transfer files instead of sequentially. When I look at
network activity on the windows machine on the other end of the
transfer, it's hitting 99% when two or more files are going at the same
time, but only about 80% when one file is going.

I don't think the bottleneck is on the particular windows machine, as it
seems to be the case with multiple windows machines that I try this on.

So, it seems to me this bottleneck is either:
* The 10/100 switch that connects the FreeBSD machine to the windows
machine(s) [I don't have a crossover cable to test this]
* The FreeBSD machine's network card [gigabit cheapo].
* The FreeBSD machine's hard drive access.

I don't think the problem is with the hard drives (ZFS raidz array of 3
drives), because when they're going at full blast it pins the CPU, and
the CPU is only at about 40% during these transfers.

So, what else would account for this behavior? Is it something in
Samba? Or is it a hardware networking issue?

Ultimately, I'm trying to decide whether or not to upgrade the 10/100
switch to a gigabit switch. But if there's a bottleneck somewhere else,
either software or hardware, I won't spend the cash to do it.

[Dominic Fandrey]

MZ wrote:
> Weird observation...
>
> When I'm transferring files to and from my 7.2 box, it goes faster when
> I simultaneously transfer files instead of sequentially. When I look at
> network activity on the windows machine on the other end of the
> transfer, it's hitting 99% when two or more files are going at the same
> time, but only about 80% when one file is going.

In my experience this is also the case with Windows<->Windows transfers.

Did you test this?

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