Reading from OMV is slow and variable, Writing is great

Hi,
After many years with FreeNas I have now made the switch to OMV. I am having one issue that is preventing me using it to serve media to my Raspberry Pi and PC for viewing.
The testing I have done, I have done on my Windows 8.1 PC, but the symptoms are the same on both the PC and my RaspberryPi, which is running OpenELEC, 4.0.3 (It think)

My setups:
OMV is on an Intel Atom DN2800MT with 4GB ram, running OMV version 0.5.49, 1Gbit on-board NIC, using SAMBA and NFS (SAMBA for these tests
PC Old DELL with Windows 8.1, 4GB Ram, 10/100Mbit on-board NIC
Raspberry Pi model B, standard, wired network, OpenELEC 4.0.3 (or whatever the latest version is
Switch is a D-LINK DGS-1224T 24 port Gigabit switch. As far as I know I haven't made any untoward settings in it.

The symptoms.
I can write ISO file x from my PC to the OMV while saturating the link at 11MB/s (it is a 100MBit card), see image 4 below. Reading the exact same file back right after, and the results are far from the same. The speed is too slow to be able to watch anything as it dropps down below 100kB/s quite frequently. I have even seen it go to 0kB/s. Another artifact is that it is very variable. Images 1-3 shows the read, with a low value, and a higher value. As can be seen in image 3, The speed did get respectable at one point, albeit not 11MB/s as far as I can make out from the chart. It does suggest it is capable of decent speeds, but just not happy to do it consistently.
On the Raspberry Pi I am also not able to watch anything as it stops and buffers very often, but I don't know how to actually test the transfer speed, so I can't give any numbers. I think it is the variability that is the killer. The average speed is probably good enough to watch a non-HD movie, but as it is not constant, I can't.

Image of transfer speeds:

What I have tried:
Even though I suspect that the issue is with the OMV part as both the Raspberry Pi and the PC shows the symptoms I have still tried some things on the PC. I have tried to disable the TCP Checksum Offloading for IPv6 (no idea what it is, but someone said it solved their issues ;-), but to no avail, so I set it back to default. I looked at Flow control, no luck. I tried turning something else off in the command line, that I can't even find the page for anymore, but that didn't work either and I set that back as well.
I have also tried swapping the network cable between the PC and the OMV box to check that it isn't a dodgy connector or lead, but the results were identical.
I have also read most of the threads I can find here that mentions un-even or poor network speeds.

My Theories...
Not much, to be honest.
1. I am sharing the same drive via Samba and NFS, could that have something to do with it?
2. I ran a test on HDD speed that I saw in a post on this forum. I wasn't able to run it on the OMV drive as I had hoped, but running it on my own drive in the PC I got the following result...
Image of HDD speeds:

Could it be that it has something to do with package sizes, as the small packets are very slow? (Doesn't explain the variability in speed though...)

I would be grateful for any suggestions of things to try!

Cheers

Thanks for your reply davidh2k.
I have only just had the time to look into things.

1. HDD speed. I tried the dd command and got the following: "4023820288 bytes (4.0 GB) copied, 116.138 s, 34.6 MB/s" Not lightning, but should be watchable

2. using the file manager in OpenELEC I copied the same file (the start of it) to a Transcend JetFlash(?) 16GB USB3 stick that is the system "drive" for the Pi. The read speed for SAMBA was topping out briefly at 1.2MB/s, mostly hovering at 1.1MB/s. Then I tried NFS which I am using on the Pi, and I got 2.2MB/s. Both are really disappointing in my humble opinion.

Just a note here, I have just mounted the NFS drives via the GUI, so not tuned in any way yet.

I will try with my laptop tomorrow, which has a GBit NIC on it as I am curious to see how high it will go when writing, but I guess I am mostly surprised that it will saturate the 100MBit link when writing to the OMV system, but then get between 10% and 20% of that when reading the same file over the same network.

Any other thoughts, as a GBit NIC is out of the question for the Pi, even if it does prove faster. Surely one should be able to read and write at similar speeds??

Cheers

Me again,
I did some more tests with my laptop, which has GBit NIC in it, and with interesting results.

Writing the same file as in my original post to the OMV machine: 50-60MB/s. Could be better I believe, but more than adequate for my needs.
Reading the same file from the OMV machine: 16-21MB/s.
This was done using Samba.

2 things I find odd here..
1. as with my 100Mbit PC, the read speed is significantly slower than writing. This ties in to my original question... Why is this? Why aren't they similar? Everything is the same except the direction of the data...
2. The OMV machine, despite being a lot slower when being read from, can obviously provide data at 16-21MB/s over the hardware / switch/ links, so why with my 100MBit machines do I only get 0.1-5MBit? (see my original post)

I would be very grateful for any ideas! I might have stuffed up some settings somewhere, but I am only to happy to be told that, as long as I am also told what to do to fix it
I have reached the end of my networking knowledge

Ps. is there some good tool for analyzing networks out there? (Things like speeds, packet failure rates etc.)

Cheers

Hi david2k and tekkbebe,
I haven't had a chance to try and rule out equipment, but it appears that the trend is the same on any of the three systems I use. Writing to the OMV machine is good, reading is bad. Yes the gigabit laptop is much faster, but it is still slow reading data.
Also, just so we are talking the same language, my numbers are all in MByte/s. (as far as I can tell anyway ) I'll see what tests I can get in this weekend.

tekkbebe, I haven't heard about the OMV extras, I'll check it out and see what comes of that. Thanks

Cheers!