File transfers over ssh limited by CPU speed

M

mix_room

I am trying to transfer some large files over the internet. Generally SSH (rsync -e ssh, scp) works wonderfully for this. BUT it turns out that the CPU is limiting the speed with which I can transfer the files. I can not get more than 1.6 MBps (~13Mbps) out of a single transfer.
Since this does not maximize my transfer capacity I would like to improve the transfer rate.

1) What I do: rsync from cygwin windows server 2008 -> FreeBSD server. Fastest rate: 13Mbps.
2) What I would like to do: rsync from cygwin windows server 2008 -> FreeBSD server. Fastest rate: 100Mbps.

Is there any way in which this can be achieved?
A) multi-threaded rsync?
B) other encryption standard on ssh (tried [cmd=""]ssh -c blowfish[/cmd] to no avail)
C) others, such as alternative transfer protocol, preferably not.

The processors are fairly new Intel Xeon, so they shouldn't be slow out of the box.
I realise that the FreeBSD forum may not be the appropriate place to ask this question as it involves running the cygwin port of ssh on windows, but was hoping that someone might have a good hint, or idea.
 
It might was well be router, that throttles everything (I had this problem, until I was able to directly connect both PC's)
 
I updated my installation of cygwin, it had an old version of openssh now at 5.6.
While this did not improve the speed, it did significantly reduce CPU-load: from 100% on a CPU-core to zero.

Now it seems that there is something else that is causing problems. I will continue to look for improved speeds, but it no longer seems to be the CPU that is limiting.
 
also check your firewall rules (if you're running firewall) baybe you have set limited bandwidth....
If possibly try to disable firewall, and see if that helps
 
killasmurf86 said:
also check your firewall rules (if you're running firewall) baybe you have set limited bandwidth.
Click to expand...
Will take a look.

If possibly try to disable firewall, and see if that helps
Click to expand...
Unfortunately not possible.


This is the only type of transfer that is limited. I am suspecting limited peering capacity between the two providers.
 
Install security/openssh-portable and enable the HPN patches. This patches OpenSSH for two things: larger transmit/receive buffers internally, enables the NONE cipher (ie not encrypted).

With that, you can eliminate the encryption for the bulk data transfer and achieve as close to the full line rate (100 Mbps) as you can get without switching to bare UDP packets.

You'll need to add the following to /etc/rc.conf:
Code: 
sshd_enable="NO"
openssh_enable="YES"

Then run the following:
# service sshd onestop
# service openssh start

The extra options to add to /usr/local/etc/ssh/sshd_config are:
Code: 
# The following are HPN-related configuration options
# Whether to disable hpn performance boosts. 
HPNDisabled no

# TCP receive buffer polling.
# Disable in non-autotuning kernels
TcpRcvBufPoll yes

# Buffer size for hpn to non-hpn connections
HPNBufferSize 8192

# Whether to allow the use of the "none" cipher
NoneEnabled yes
You'll need to play with the HPNBufferSize to match it up to your system. 8192 is a good value for gigabit links.

Connecting from a non-HPN ssh client to an HPN-enabled server will give you about 10-20% speed increase.

Connectiong from an HPN-enabled client to an HPN-enabled server will give you about a 15-30% increase.

Connecting from an HPN-enabled client using NONE cipher to HPN-enabled server will give about a 50% increase.

To use the NONE cipher, you have to manually specify it on the SSH commandline:
$ /usr/local/bin/ssh -oNoneEnabled=yes -oNoneSwitch=yes -oHPNBufferSize=8192 username@host
$ /usr/local/bin/scp -oNoneEnabled=yes -oNoneSwitch=yes -oHPNBufferSize=8192 username@host

To use it with rsync:
$ rsync --rsh="/usr/local/bin/scp -oNoneEnabled=yes -oNoneSwitch=yes -oHPNBufferSize=8192" --other-rsync-options ...

We use this on our rsync servers. Can almost get 100 MBps out of SATA disks across a gigabit fibre link.
 
Has the procedure for HPN enablement changed in the last few years? I have ticked
Code: 
Enable HPN-SSH patch
in the options for openssh-portable-overwrite-base 5.2.p1_4,1 (along with
Code: 
OVERWRITE_BASE
)

I then, as described above, modified
Code: 
sshd_config
as above. However, the options are flagged as bad, for example:

Enabling
Code: 
# The following are HPN-related configuration options
# Whether to disable hpn performance boosts.
HPNDisabled no

Yields

Code: 
Bad configuration option: HPNDisabled

on
Code: 
service openssh restart
and OpenSSH does not start. Commenting the HPN specific options out of
Code: 
sshd_config
and executing
Code: 
service openssh restart
yields expected results.

Are there no HPN specific options configurable in 5.2.p1_4,1?
 
Absent further configuration of HPN, simply enabling or disabling the HPN-SSH patch and copying files using WinSCP 4.3.4 across 100mbit LAN, I got the following results:

Code: 
Protocol  HPN  Cipher    Data Rate (mB/sec)
SCP       Yes  AES       7.8
SCP       No   AES       7.9
SCP       No   BlowFish  8.2
SCP       Yes  BlowFish  8.1
SFTP      No   BlowFish  6.9
SFTP      No   AES       5.7
SFTP      Yes  AES       5.8
SFTP      Yes  BlowFish  7.0
Which suggest that the HPN option as enabled and absent setting the tuning options described above slightly degrades SCP performance and slightly improves SFTP performance. Other results are about as expected.
 
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