Re: NFS4 file transfers fail or are very slow

[Michael <pikim@web.de>]

Am 17.01.2018 um 16:37 schrieb Dan Ritter:
> On Tue, Jan 16, 2018 at 11:41:05PM +0100, Michael wrote:
>> Hello guys,
>>
>> I have recently installed Debian Stretch 9.3 on a new PC and I'd 
just like
>> to provide some NFS shares for other Linux machines in the LAN 
(1GBit). With
>> small files everything works fine, but if I try to copy, e.g., a 7GB 
file
>> with rsync it starts with a high transmission rate above 160MB/s and 
then
>> goes down to around 70-90MB/s. After a random but short time there's 
no more
>> progress going on for about 10-15 seconds. When the process then 
continues,
>> the speed goes down to around 20MB/s and then up to about 200MB/s. 
It seems
>> to continue transferring data, but rsync gives me an error message 
in the
>> end.
>
> Max throughput on 1Gb/s ethernet is slightly less than 125 MB
> per second. Bits versus bytes, you know.
>
> Anytime you see a rate above that, you're actually seeing
> compression ratios rather than on-the-line bytes. Rsync is doing
> that for you,
>
> 90MB/s is a normalish large-file transfer rate for
> not-very-compressible data being read off of a spinning disk.

Just for clarification: my given rates were read from SSD and written to a
spinning disk (WD Red).

> rsync also makes an awful lot of disk seeks in the attempt to
> not transfer data that it doesn't need to transfer.

But it does that via NFS as well as via SMB, doesn't it?

>> Exactly the same share is able to write more than 105MB/s via 
SMB/CIFS, so I
>> would expect an NFS speed in a similar range.
>
> Protocol overhead. Have you tried running a network benchmark?

I installed and ran iperf, but I don't know whether that provides 
reasonable
results:
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[  4] local 192.168.192.10 port 5001 connected with 192.168.192.20 port 
44282
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.0 sec  1.09 GBytes   936 Mbits/sec

When I copy the same file 3 times onto the same share I get an average of
108 MB/s with SMB/CIFS
 84 MB/s with NFS (async,no_subtree_check)

But in many/most comparisons you can find in the internet, NFS is having a
higher performance. So isn't that the case in real worldapplications?

> -dsr-
Michael