Re: NFS4 file transfers fail or are very slow
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.
rsync also makes an awful lot of disk seeks in the attempt to
not transfer data that it doesn't need to transfer.
> 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?
-dsr-
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