Re: Debian server for backups of Windows clients
On Sat, Sep 10, 2016 at 01:22:45AM -0400, Neal P. Murphy wrote:
> On Fri, 9 Sep 2016 23:14:30 -0500
> David Wright <deblis@lionunicorn.co.uk> wrote:
>
> Good eye! I was going to say it's not possible to get 110Mb/s over 802.11g; 40-50 is closer tothe best I get. And 193Mb/s over 100Mb/s ethernet is right out; best I've ever managed is maybe 97Mb/s, and 92-95 is more typical. 11,034,157Mb/s on W/L and 19,338,838Mb/s on wired is *much* more believable.
>
> Unless one has a very fast multicore CPU with hardware crypto assistance, very fast RAM and the data to be transferred cached in RAM, one will probably never saturate a fastE or gigE link where one end must decrypt the data from disk/cache then encrypt the data to scp, and the other end must decrypt the data from scp then encrypt the data to disk. Even simple compression slows transfer down far too much.
SSDs can routinely read 400-600 MB/s. No need to have everything
cached in RAM.
In 2010, the first generation of i5 CPUs with hardware support for AES
could encrypt at about 15 MB/s, more than filling a 100 Mb/s pipe.
Here's a table of recent CPUs with AES support, running with
OpenSSL/LibreSSL. https://calomel.org/aesni_ssl_performance.html
It's in megabytes per second, so assume 1000/8 = 250 MB/s is the
bandwidth of a gigabit ethernet NIC. Anything which can do 2x
that can approach encrypting/decrypting from SSD, then
decrypting/encrypting over an SSH connection.
There are a lot of 500s and above on that chart.
And that's per-core, so even the 250+ CPUs can fill a gig-e pipe
while reading from SSD.
Nor are they monstrously expensive: an AMD FX-6300 is $90, a
motherboard for it could be another $90, and you can get a
decent SSD for $100 these days. A $400 desktop can be put
together that can saturate a gig-E link with encrypted traffic
from an encrypted disk.
Truly we live in marvelous times.
-dsr-
Reply to: