Rsyncing via LAN deadly slow

[raf]

F27AE.9000301 at free.fr>

Stephane Ascoet via rsync wrote:

> Hi, I'm backing up contents of my GOBook(http://sascoet.mutu.fdn.fr/monalbum/albums/sa-12082010fujitsugigamos2300scsifleury-les-aubraisrecusdemonsauveurcomputermagneticsdmc-lx2/sa-1208201012h39fujitsugigamo2300scsiconnecteagobookfleury-les-aubraisrecusdemonsauveurcomputermagneticsdmc-lx2.jpg)
> before it dies completely on a dell laptop via my LAN(netstat indicates a
> 11.8MB/s speed between the two computers via this one).
> 
> On the GOBook I launch "rsync --daemon"(3.1.1-3 version)
> 
> On the dell: rsync -abSbHXz --progress(3.1.2-1 version)
> 
> CPUs are doing almost nothing. So does the GOBook HDD. The destination is on
> a mounted logical volume in Ext2 on a nvme SSD.
> 
> And the indicated speed transfer is around 50kB/s!!! I tried -W option: it's
> even slower. Same thing when I put off the "z"(anyway, CPUs aren't doing
> nothing).
> 
> If I netstat during the backup, it appears that there is about 4MB/s used,
> so almost 100 times more than the actual data written on destination! And
> why not 11MB/s since my network can do it?
> 
> I spent hours searching an explanation on the Web, nothing explaining what's
> happening in a sufficient satisfaying way for me. Does somenone on this list
> have a clue?
> 
> -- 
> Sincerely, Stephane Ascoet

Hi, I probably can't help. The only time I had rsync
being slow enough to bother me, it was being slowed
down by ssh's encryption, but that was a long time ago,
and you're not even using ssh. The only thing I can
suggest is that your network bandwidth is being used up
by something else (whatever is using up that 4MB/s) but
that sounds unlikely, and even so, there should still
be another 8MB/s to spare. Wireshark could help you
identify what the traffic is.

I just saw the picture. It looks super old. Perhaps the
problem is the disk I/O speed on the gobook itself. Is
that possible? I have no idea how old it is or what old
I/O speeds were like. Can you run top on the gobook? Is
there iowait? If so, that might be the problem. Also,
if the gobook is really old, its network interface
might only be 10Mbps, but even that should mean 1.25MB/s
(if the disk I/O speed can keep up).

My advice is to let it run now while it still can. :-)
Or you could try scp just to see if the transfer speed
is any different.

cheers,
raf