Network Speed on Linux NAS underperforming, how to debug (it's not the cables)
before posting this I read many threads/pages/blogs about networks speeds underperforming the specs. So I bought new CAT6 UTP cables and tested between every device on my network.
I now get consistent speeds at around 110mb/s between all devices except my self-build linux NAS. It consistently copies files only at 40mb/s. I tested this with short cables, long cables, a dedicated 1gbit switch (instead of my gigabit router doing the routing), always the same result. I tested copying over the network from SSD to SSD, SSD to HDD, no difference (NAS has both SSD and HDD). I tried SFTP, SMB, FTP, also made no difference. In all tests the NAS' load stayed very small.
By now my suspicion is the NAS hardware and/or linux drivers, configuration. How can I debug this?
[update]
1 core maxes out during file copy over network. the load seemed small at 0,6 in munin but thats just the average over 5min. So CPU is the bottleneck?
[update 2]
so in my case the driver helped a bit but at the end my bottleneck is the combination of protocol+cpu. only HTTP manages to max out the connection whereas sftp and smb are limited by the cpu, maybe some tweaking can reduce cpu-usage for either for them.
The Specs:
OS: Debian 8
Board: ASRock N3150B-ITX Intel N3150 mITX
CPU: Intel(R) Celeron(R) CPU N3150 @ 1.60GHz
RAM: 8 GB
HDD: 2 x WD Red WD40EFRX 4TB
SSD: 1 x Kingston SSDNow V300 120GB MLC
Detailed Specs
lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 4
On-line CPU(s) list: 0-3
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 76
Model name: Intel(R) Celeron(R) CPU N3150 @ 1.60GHz
Stepping: 3
CPU MHz: 481.933
CPU max MHz: 2080,0000
CPU min MHz: 480,0000
BogoMIPS: 3202.01
Virtualization: VT-x
L1d cache: 24K
L1i cache: 32K
L2 cache: 1024K
NUMA node0 CPU(s): 0-3
lshw
description: Computer
width: 64 bits
capabilities: smbios-2.8 vsyscall32
*-core
description: Motherboard
physical id: 0
*-memory
description: System memory
physical id: 0
size: 7472MiB
*-cpu
product: Intel(R) Celeron(R) CPU N3150 @ 1.60GHz
vendor: Intel Corp.
physical id: 1
bus info: cpu@0
size: 479MHz
capacity: 2080MHz
width: 64 bits
capabilities: fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp x86-64 constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 movbe popcnt tsc_deadline_timer aes rdrand lahf_lm 3dnowprefetch epb tpr_shadow vnmi flexpriority ept vpid tsc_adjust smep erms dtherm ida arat cpufreq
*-pci
description: Host bridge
product: Intel Corporation
vendor: Intel Corporation
physical id: 100
bus info: pci@0000:00:00.0
version: 21
width: 32 bits
clock: 33MHz
configuration: driver=iosf_mbi_pci
resources: irq:0
*-display
description: VGA compatible controller
product: Intel Corporation
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 21
width: 64 bits
clock: 33MHz
capabilities: pm msi vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
resources: irq:121 memory:90000000-90ffffff memory:80000000-8fffffff ioport:f000(size=64) memory:c0000-dffff
*-storage
description: SATA controller
product: Intel Corporation
vendor: Intel Corporation
physical id: 13
bus info: pci@0000:00:13.0
version: 21
width: 32 bits
clock: 66MHz
capabilities: storage msi pm ahci_1.0 bus_master cap_list
configuration: driver=ahci latency=0
resources: irq:118 ioport:f060(size=32) memory:91415000-914157ff
*-usb
description: USB controller
product: Intel Corporation
vendor: Intel Corporation
physical id: 14
bus info: pci@0000:00:14.0
version: 21
width: 64 bits
clock: 33MHz
capabilities: pm msi xhci bus_master cap_list
configuration: driver=xhci_hcd latency=0
resources: irq:117 memory:91400000-9140ffff
*-usbhost:0
product: xHCI Host Controller
vendor: Linux 4.8.0-0.bpo.2-amd64 xhci-hcd
physical id: 0
bus info: usb@1
logical name: usb1
version: 4.08
capabilities: usb-2.00
configuration: driver=hub slots=7 speed=480Mbit/s
*-usb
description: USB hub
product: USB2.0 Hub
vendor: Genesys Logic, Inc.
physical id: 5
bus info: usb@1:5
version: 88.31
capabilities: usb-2.00
configuration: driver=hub maxpower=100mA slots=4 speed=480Mbit/s
*-usbhost:1
product: xHCI Host Controller
vendor: Linux 4.8.0-0.bpo.2-amd64 xhci-hcd
physical id: 1
bus info: usb@2
logical name: usb2
version: 4.08
capabilities: usb-3.00
configuration: driver=hub slots=6 speed=5000Mbit/s
*-generic UNCLAIMED
description: Encryption controller
product: Intel Corporation
vendor: Intel Corporation
physical id: 1a
bus info: pci@0000:00:1a.0
version: 21
width: 32 bits
clock: 33MHz
capabilities: pm msi bus_master cap_list
configuration: latency=0
resources: memory:91100000-911fffff memory:91000000-910fffff
*-multimedia
description: Audio device
product: Intel Corporation
vendor: Intel Corporation
physical id: 1b
bus info: pci@0000:00:1b.0
version: 21
width: 64 bits
clock: 33MHz
capabilities: pm msi bus_master cap_list
configuration: driver=snd_hda_intel latency=0
resources: irq:122 memory:91410000-91413fff
*-pci:0
description: PCI bridge
product: Intel Corporation
vendor: Intel Corporation
physical id: 1c
bus info: pci@0000:00:1c.0
version: 21
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:115 ioport:e000(size=4096) memory:91300000-913fffff
*-storage
description: SATA controller
product: 88SE9128 PCIe SATA 6 Gb/s RAID controller
vendor: Marvell Technology Group Ltd.
physical id: 0
bus info: pci@0000:01:00.0
version: 20
width: 32 bits
clock: 33MHz
capabilities: storage pm msi pciexpress ahci_1.0 bus_master cap_list rom
configuration: driver=ahci latency=0
resources: irq:120 ioport:e050(size=8) ioport:e040(size=4) ioport:e030(size=8) ioport:e020(size=4) ioport:e000(size=32) memory:91310000-913107ff memory:91300000-9130ffff
*-pci:1
description: PCI bridge
product: Intel Corporation
vendor: Intel Corporation
physical id: 1c.1
bus info: pci@0000:00:1c.1
version: 21
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:116 ioport:d000(size=4096) memory:91200000-912fffff
*-network
description: Ethernet interface
product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:02:00.0
logical name: eth0
version: 11
serial: d0:50:99:78:03:d2
size: 1Gbit/s
capacity: 1Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168g-2_0.0.1 02/06/13 ip=192.168.0.100 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s
resources: irq:119 ioport:d000(size=256) memory:91204000-91204fff memory:91200000-91203fff
*-isa
description: ISA bridge
product: Intel Corporation
vendor: Intel Corporation
physical id: 1f
bus info: pci@0000:00:1f.0
version: 21
width: 32 bits
clock: 33MHz
capabilities: isa bus_master cap_list
configuration: driver=lpc_ich latency=0
resources: irq:0
*-serial
description: SMBus
product: Intel Corporation
vendor: Intel Corporation
physical id: 1f.3
bus info: pci@0000:00:1f.3
version: 21
width: 32 bits
clock: 33MHz
capabilities: pm cap_list
configuration: driver=i801_smbus latency=0
resources: irq:18 memory:91414000-9141401f ioport:f040(size=32)
*-scsi:0
physical id: 2
logical name: scsi0
capabilities: emulated
*-disk
description: ATA Disk
product: KINGSTON SV300S3
physical id: 0.0.0
bus info: scsi@0:0.0.0
logical name: /dev/sda
version: BBF0
serial: 50026B7854011055
size: 111GiB (120GB)
capabilities: gpt-1.00 partitioned partitioned:gpt
configuration: ansiversion=5 guid=bd0d92d8-3872-4af8-bd37-6e144769d696 logicalsectorsize=512 sectorsize=512
*-volume:0
description: Windows FAT volume
vendor: mkfs.fat
physical id: 1
bus info: scsi@0:0.0.0,1
logical name: /dev/sda1
logical name: /boot/efi
version: FAT32
serial: a00b-19c0
size: 510MiB
capacity: 511MiB
capabilities: boot fat initialized
configuration: FATs=2 filesystem=fat mount.fstype=vfat mount.options=rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro state=mounted
*-volume:1
description: EXT4 volume
vendor: Linux
physical id: 2
bus info: scsi@0:0.0.0,2
logical name: /dev/sda2
logical name: /
version: 1.0
serial: 3c53dc3f-51e0-4967-810a-46642c6dba53
size: 103GiB
capabilities: journaled extended_attributes large_files huge_files dir_nlink recover extents ext4 ext2 initialized
configuration: created=2017-01-03 17:06:08 filesystem=ext4 lastmountpoint=/ modified=2017-02-08 22:31:35 mount.fstype=ext4 mount.options=rw,relatime,errors=remount-ro,data=ordered mounted=2017-02-08 22:31:36 state=mounted
*-volume:2
description: Linux swap volume
vendor: Linux
physical id: 3
bus info: scsi@0:0.0.0,3
logical name: /dev/sda3
version: 1
serial: 3e37cb96-5f81-48d1-be5b-ca47292b232f
size: 7665MiB
capacity: 7666MiB
capabilities: nofs swap initialized
configuration: filesystem=swap pagesize=4095
*-scsi:1
physical id: 3
logical name: scsi2
capabilities: emulated
*-disk
description: ATA Disk
product: WDC WD40EFRX-68N
vendor: Western Digital
physical id: 0.0.0
bus info: scsi@2:0.0.0
logical name: /dev/sdb
version: 0A82
serial: WD-WCC7K7HFN3K7
size: 3726GiB (4TB)
configuration: ansiversion=5 logicalsectorsize=512 sectorsize=4096
*-scsi:2
physical id: 4
logical name: scsi3
capabilities: emulated
*-disk
description: ATA Disk
product: WDC WD40EFRX-68N
vendor: Western Digital
physical id: 0.0.0
bus info: scsi@3:0.0.0
logical name: /dev/sdc
version: 0A82
serial: WD-WCC7K1XSZYZ6
size: 3726GiB (4TB)
configuration: ansiversion=5 logicalsectorsize=512 sectorsize=4096
*-scsi:3
physical id: 5
logical name: scsi9
capabilities: emulated
*-processor UNCLAIMED
description: SCSI Processor
physical id: 0.0.0
bus info: scsi@9:0.0.0
*-network:0
description: Ethernet interface
physical id: 1
logical name: vethBC83V0
serial: fe:72:5a:77:15:f2
size: 10Gbit/s
capabilities: ethernet physical
configuration: autonegotiation=off broadcast=yes driver=veth driverversion=1.0 duplex=full link=yes multicast=yes port=twisted pair speed=10Gbit/s
*-network:1
description: Ethernet interface
physical id: 2
logical name: veth4IKF6U
serial: fe:a4:7f:d9:88:e8
size: 10Gbit/s
capabilities: ethernet physical
configuration: autonegotiation=off broadcast=yes driver=veth driverversion=1.0 duplex=full link=yes multicast=yes port=twisted pair speed=10Gbit/s
*-network:2
description: Ethernet interface
physical id: 3
logical name: veth6FWFI5
serial: fe:26:a4:3e:ec:22
size: 10Gbit/s
capabilities: ethernet physical
configuration: autonegotiation=off broadcast=yes driver=veth driverversion=1.0 duplex=full link=yes multicast=yes port=twisted pair speed=10Gbit/s
*-network:3 DISABLED
description: Ethernet interface
physical id: 4
logical name: lxc-nic
serial: 52:54:00:c6:f0:23
size: 10Mbit/s
capabilities: ethernet physical
configuration: autonegotiation=off broadcast=yes driver=tun driverversion=1.6 duplex=full link=no multicast=yes port=twisted pair speed=10Mbit/s
hwinfo --short
cpu:
Intel(R) Celeron(R) CPU N3150 @ 1.60GHz, 480 MHz
Intel(R) Celeron(R) CPU N3150 @ 1.60GHz, 480 MHz
Intel(R) Celeron(R) CPU N3150 @ 1.60GHz, 480 MHz
Intel(R) Celeron(R) CPU N3150 @ 1.60GHz, 480 MHz
graphics card:
Intel VGA compatible controller
sound:
Intel Audio device
storage:
Intel SATA controller
Marvell 88SE9128 PCIe SATA 6 Gb/s RAID controller
network:
eth0 Realtek RTL8111/8168 PCI Express Gigabit Ethernet controller
network interface:
veth6FWFI5 Ethernet network interface
lxc Ethernet network interface
eth0 Ethernet network interface
vethBC83V0 Ethernet network interface
lxc-nic Ethernet network interface
lo Loopback network interface
veth4IKF6U Ethernet network interface
disk:
/dev/sdb WDC WD40EFRX-68N
/dev/sdc WDC WD40EFRX-68N
/dev/sda KINGSTON SV300S3
partition:
/dev/sda1 Partition
/dev/sda2 Partition
/dev/sda3 Partition
usb controller:
Intel USB Controller
bios:
BIOS
bridge:
Intel Host bridge
Intel PCI bridge
Intel PCI bridge
Intel ISA bridge
hub:
Linux 4.8.0-0.bpo.2-amd64 xhci-hcd xHCI Host Controller
Genesys Logic USB2.0 Hub
Linux 4.8.0-0.bpo.2-amd64 xhci-hcd xHCI Host Controller
memory:
Main Memory
unknown:
FPU
DMA controller
PIC
Keyboard controller
/dev/lp0 Parallel controller
PS/2 Controller
Intel SMBus
Intel Encryption controller
/dev/ttyS0 16550A
/dev/ttyS1 16550A
/dev/sg3 Marvell 91xx Config
lspci
00:00.0 Host bridge: Intel Corporation Device 2280 (rev 21)
00:02.0 VGA compatible controller: Intel Corporation Device 22b1 (rev 21)
00:13.0 SATA controller: Intel Corporation Device 22a3 (rev 21)
00:14.0 USB controller: Intel Corporation Device 22b5 (rev 21)
00:1a.0 Encryption controller: Intel Corporation Device 2298 (rev 21)
00:1b.0 Audio device: Intel Corporation Device 2284 (rev 21)
00:1c.0 PCI bridge: Intel Corporation Device 22c8 (rev 21)
00:1c.1 PCI bridge: Intel Corporation Device 22ca (rev 21)
00:1f.0 ISA bridge: Intel Corporation Device 229c (rev 21)
00:1f.3 SMBus: Intel Corporation Device 2292 (rev 21)
01:00.0 SATA controller: Marvell Technology Group Ltd. 88SE9128 PCIe SATA 6 Gb/s RAID controller (rev 20)
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 11)
ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether d0:50:99:78:03:d2 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.100/24 brd 192.168.0.255 scope global eth0
valid_lft forever preferred_lft forever
5: lxc: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether 52:54:00:c6:f0:23 brd ff:ff:ff:ff:ff:ff
inet 10.11.0.1/24 brd 10.11.0.255 scope global lxc
valid_lft forever preferred_lft forever
6: lxc-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master lxc state DOWN group default qlen 1000
link/ether 52:54:00:c6:f0:23 brd ff:ff:ff:ff:ff:ff
12: veth6FWFI5@if11: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master lxc state UP group default qlen 1000
link/ether fe:26:a4:3e:ec:22 brd ff:ff:ff:ff:ff:ff
inet6 fe80::fc26:a4ff:fe3e:ec22/64 scope link
valid_lft forever preferred_lft forever
16: veth4IKF6U@if15: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master lxc state UP group default qlen 1000
link/ether fe:a4:7f:d9:88:e8 brd ff:ff:ff:ff:ff:ff
inet6 fe80::fca4:7fff:fed9:88e8/64 scope link
valid_lft forever preferred_lft forever
38: vethBC83V0@if37: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master lxc state UP group default qlen 1000
link/ether fe:72:5a:77:15:f2 brd ff:ff:ff:ff:ff:ff
inet6 fe80::fc72:5aff:fe77:15f2/64 scope link
valid_lft forever preferred_lft forever
ethtool eth0
Settings for eth0:
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised pause frame use: Symmetric Receive-only
Advertised auto-negotiation: Yes
Link partner advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Link partner advertised pause frame use: Symmetric
Link partner advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: MII
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000033 (51)
drv probe ifdown ifup
Link detected: yes
iptables
iptables -L -n -v --line-numbers
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 1280K 89M fail2ban-ssh tcp -- * * 0.0.0.0/0 0.0.0.0/0 multiport dports 22
2 0 0 ACCEPT udp -- lxc * 0.0.0.0/0 0.0.0.0/0 udp dpt:53
3 0 0 ACCEPT tcp -- lxc * 0.0.0.0/0 0.0.0.0/0 tcp dpt:53
4 0 0 ACCEPT udp -- lxc * 0.0.0.0/0 0.0.0.0/0 udp dpt:67
5 0 0 ACCEPT tcp -- lxc * 0.0.0.0/0 0.0.0.0/0 tcp dpt:67
6 615K 107M ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
7 0 0 REJECT all -- !lo * 0.0.0.0/0 127.0.0.0/8 reject-with icmp-port-unreachable
8 7065K 1431M ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
9 40 2560 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.100 state NEW tcp dpt:22
10 27 1724 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.100 state NEW tcp dpt:80
11 15377 923K ACCEPT tcp -- * * 10.11.0.10 10.11.0.1 state NEW tcp dpt:4949
12 340K 65M ACCEPT udp -- * * 192.168.0.0/24 0.0.0.0/0 state NEW udp dpt:5353
13 0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.100 state NEW tcp dpt:3689
14 0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.100 state NEW tcp dpt:6600
15 5 412 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
16 309K 77M LOG all -- * * 0.0.0.0/0 0.0.0.0/0 limit: avg 5/min burst 5 LOG flags 0 level 7 prefix "iptables denied: "
17 441K 97M DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 429 38624 ACCEPT tcp -- * * 0.0.0.0/0 10.11.0.20 state NEW tcp dpt:445
2 7 444 ACCEPT tcp -- * * 0.0.0.0/0 10.11.0.20 state NEW tcp dpt:139
3 0 0 ACCEPT udp -- * * 0.0.0.0/0 10.11.0.20 state NEW udp dpt:138
4 2 156 ACCEPT udp -- * * 0.0.0.0/0 10.11.0.20 state NEW udp dpt:137
5 243M 228G ACCEPT all -- * lxc 0.0.0.0/0 10.11.0.0/24 ctstate RELATED,ESTABLISHED
6 84M 341G ACCEPT all -- lxc * 10.11.0.0/24 0.0.0.0/0
7 0 0 ACCEPT all -- lxc lxc 0.0.0.0/0 0.0.0.0/0
8 0 0 REJECT all -- * lxc 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
9 0 0 REJECT all -- lxc * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable
10 0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination
1 0 0 ACCEPT udp -- * lxc 0.0.0.0/0 0.0.0.0/0 udp dpt:68
2 12M 9842M ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
Chain fail2ban-ssh (1 references)
num pkts bytes target prot opt in out source destination
1 1280K 89M RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
greenone831 Answer
update
It seems my hypothesis, below, had merit: here you will find a recent guide on how to correct the 8168 behaviour by installing the appropriate drivers, and how to make them stick after a kernel upgrade/reboot.
protocols
Using a protocol such as SFTP implies adding encryption and compression. Compressing a file means that you hit the CPU, but increase the network bandwidth. Which is itself, on a slow CPU, influenced by CPU load. So you need to strike a balance between the two.
The relevant settings are the same as SSH and SCP. You want to experiment with different ciphers, because each implementation is machine dependant.
Also, network configuration for short-latency, large-bandwidth connections is different than the reverse. Linux has auto-tuning, but still your situation might fall outside its limits; here you'll find some more information (and where to tweak). I remember seeing a script that claimed to do auto-tuning by transferring a large file between two hosts (one in server mode, one in client mode), but to do this you need two Linux hosts. And also, importantly, the best settings for talking to a Linux SFTP host might be very bad for a Samba connection to Windows 7, and so on.
In all likelihood, you will have to find a compromise between the various needs.
original answer
network: eth0 Realtek RTL8111/8168 PCI Express Gigabit Ethernet controller ... driver=r8169
You're probably using an underperforming driver, that does not take advantage of the Realtek features (such as checksum offloading), resulting in excessive CPU load.
Here there are instructions on how to shoehorn the r8168 driver in:
You can install a dkms package with r8168 driver from official Ubuntu repositories.
You will need to uninstall the driver you have installed manually, then run in terminal:
sudo apt-get install r8168-dkmsThe dkms package will rebuild the kernel module (driver) each time you upgrade a kernel.
The repository for Ubuntu 14.04 contains a dkms r8168 version 8.037.00-1.
It may work OK. But if you really need the latest driver, you can install it by:
wget http://mirrors.kernel.org/ubuntu/pool/universe/r/r8168/r8168-dkms_8.040.00-1_all.deb sudo dpkg -i r8168-dkms_8.040.00-1_all.debThat will install the same version that you are using now but with dkms support.
Another thing you might do is activate Large Frame support (you now have the standard MTU of 1500). For large file transfers, a MTU of up to 9000 may yield better results, provided that the driver and all involved parties support it likewise.
LSerni
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