Slow transfer speed. Where's the bottleneck ?

I have OVM installed on a HP Microserver N40L, but I haven't been able to obtain good transfer speeds, so I'm trying to find the bottleneck.

I'm getting around 30-40 Mbps on transfers over my local network (everything is Gigabit, read on) on Samba, Nfs and FTP shares alike.

I have been playing around and tweaking for a while, following the advice I could find on forums, but haven't been able to improve the speed.

First of I have two Hitachi 1TB drives on software RAID1. These are working at reasonable speed :

/dev/vdb:
 Timing cached reads:   2092 MB in  2.00 seconds = 1045.39 MB/sec
 Timing buffered disk reads: 400 MB in  3.02 seconds = 132.64 MB/sec


root@openmediavault:~# hdparm -tT /dev/vdc


/dev/vdc:
 Timing cached reads:   1928 MB in  2.00 seconds = 963.62 MB/sec
 Timing buffered disk reads: 400 MB in  3.01 seconds = 132.75 MB/sec

Network cards, modem, cables, everything is ok with Gigabit speed, which I can achieve between my computer and the OVM server with iperf :

root@openmediavault:~# iperf -s
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[  4] local 192.168.1.67 port 5001 connected with 192.168.1.40 port 58598
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.1 sec    132 MBytes    110 Mbits/sec

On the server side, CPU is barely at 30-50% max on transfers, and RAM about 5-10%, so this shouldn't be a problem.

I have tried to tweak the configurations of the various transfer protocols (especially Samba, but also NFS) to obtain better speeds, but I haven't succeed.

Does anybody have a clue of where the bottleneck might be?

Has anyone gotten close to 100Mbps? If yes, which protocol have you used for the shares?

Thanks!

P.S. : The /dev/vdb and /dev/vdc is because I am currently running OVM on a ProxMox virtual machine, but I was getting the same speeds of the test below when I had OVM installed directly on the server. Actually I tried the VM to get better performance, but the speeds look the same on every step of the test I did with both.

Hi David, and thanks for your reply.

I have 28Gb of free space, so I run your test with 20Gb instead of 30 :

root@openmediavault:/media/d7bf3c48-664c-4f78-b087-88a4f570ac73# dd if=/dev/zero of=tempfile bs=1M count=20480
20480+0 records in
20480+0 records out
21474836480 bytes (21 GB) copied, 239.674 s, 89.6 MB/s


root@openmediavault:/media/d7bf3c48-664c-4f78-b087-88a4f570ac73# dd if=tempfile of=/dev/zero bs=1M count=20480
20480+0 records in
20480+0 records out
21474836480 bytes (21 GB) copied, 215.056 s, 99.9 MB/s

I think the speed could be lower than usual because of the size of the file in regard of the free space left and fragmentation issues. With a 5Gb file I get better transfer rates.

root@openmediavault:/media/d7bf3c48-664c-4f78-b087-88a4f570ac73# dd if=/dev/zero of=tempfile bs=1M count=5120
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB) copied, 49.9245 s, 108 MB/s


root@openmediavault:/media/d7bf3c48-664c-4f78-b087-88a4f570ac73# dd of=/dev/zero if=tempfile bs=1M count=5120
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB) copied, 44.9963 s, 119 MB/s

Regards,

Arduino

fizze: you're right, I will look up to see what's going on with my link. Nevertheless I would be happy to get 100 Mbps on Samba transfers, and looking to iperf output there seems to be room to improve from the 30-40 Mbps I'm getting to the 110 Mbps on iperf.

The network could indeed be the issue, as I have found strange results on network speeds.

OVM is on 192.168.1.67
My pc in 192.168.1.40
Server is 192.168.1.55

I get poor iperf from 192.168.1.40 connecting to both 192.168.1.67 and 192.168.1.55 :

iperf -c 192.168.1.67
------------------------------------------------------------
Client connecting to 192.168.1.67, TCP port 5001
TCP window size: 84.5 KByte (default)
------------------------------------------------------------
[  3] local 192.168.1.40 port 36707 connected with 192.168.1.67 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   145 MBytes   122 Mbits/sec

iperf -c 192.168.1.55
------------------------------------------------------------
Client connecting to 192.168.1.55, TCP port 5001
TCP window size: 21.6 KByte (default)
------------------------------------------------------------
[  3] local 192.168.1.40 port 56930 connected with 192.168.1.55 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   265 MBytes   222 Mbits/sec

But a lot better the other way around :

iperf -c 192.168.1.40
------------------------------------------------------------
Client connecting to 192.168.1.40, TCP port 5001
TCP window size: 16.0 KByte (default)
------------------------------------------------------------
[  3] local 192.168.1.67 port 48753 connected with 192.168.1.40 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  1.08 GBytes    923 Mbits/sec

iperf -c 192.168.1.40
------------------------------------------------------------
Client connecting to 192.168.1.40, TCP port 5001
TCP window size: 23.8 KByte (default)
------------------------------------------------------------
[  3] local 192.168.1.55 port 48844 connected with 192.168.1.40 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  1.07 GBytes   919 Mbits/sec

I got my hands on a Windows 7 machine and got 90-110 Mbps reading from the same Samba share and around 80 Mbps copying to it.

So it is indeed a problem coming from my pc (Debian 7), I'll look into it and try to figure it out. OVM seems to be working great, so that's reassuring because I can stop wasting my time trying to tweak the server.

So, as far as OVM is concerned the issue is solved. Thanks for your advice, now I know where to look...

@tekkbebe : my switch sees a Gigabit connection coming from my pc, but I'm going to investigate known issues related to my nic.