SOLVED Transfer speed drops after the first trasfer

[costaandrea]

Good afternoon to everyone,
I'am new to FreeNAS and I'm struggling with some strange network behaviour and low trasfer speed.
I upgraded my old configuration to meet a "decent" quality for running a home backup server without any big expectations.
I use Dell T1600 workstation with Xeon 31225 processor, 12 Gb of RAM, 1 pool with 5 x 500Gb WD Blue hard disks RAID z and and Intel Gigabit network card.
The machine is connected to a gigabit switch integrated into the router.
After setting up the pool I transferred a 50 Gb of files to the pool with max speed about 50 MB/s (first peak in the graphs attached). Then I tried again and suddendly the speed dropped to about 4 MB/s (second lower peak). After restarting the router I managed to get a speed upgrade but only to 8 MB/s (third peak). Now is again capped at 4 MB/s.
Do you think that the problem could be the router and its integrated switch? Or there can be other solutions?

Thank you in advance for any advise

 

[c77dk]

My first thought was SMR drives, but it seems the 500GB Blue only comes in CMR, so that part should be ok.

Try testing the throughput between TrueNAS and client using iperf3 to check the raw network speed.

 

[costaandrea]

That's the output of iperf

Code:

C:\Users\andre\Downloads\iperf-2.0.9-win64\iperf-2.0.9-win64>iperf -c 192.168.68.107 -p 5001 -f m
------------------------------------------------------------
Client connecting to 192.168.68.107, TCP port 5001
TCP window size: 0.20 MByte (default)
------------------------------------------------------------
[  3] local 192.168.68.111 port 50493 connected with 192.168.68.107 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  41.2 MBytes  34.4 Mbits/sec

That is pretty disappointing.... any suggestion?

 

[costaandrea]

I tried to switch to another gigabit switch and verified that everything was connected via cat.5e cables..... that's the result

Code:

Client connecting to 192.168.68.107, TCP port 5001
TCP window size: 0.12 MByte
------------------------------------------------------------
[  3] local 192.168.68.113 port 65444 connected with 192.168.68.107 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   112 MBytes  94.1 Mbits/sec

This is better but far beyond the expectations and it does not explain why I was able to trasfer at >150Mbits/sec in the first attempt.

 

[costaandrea]

And now that's the better part... after switching back again to the old configuration I am transferring at 200 Mbits/sec.... I am really withou any ideas...

 

[c77dk]

It sounds like the switch/router might be the issue here - a lot of the consumer sytems are quite bad. Try testing with the server and workstation conencted directly. If that works without issues, then it's time to get a better switch (quite nice switches are cheap today)

 

[Jessep]

Is any leg going over wireless or are they all wired?

 

[ChrisRJ]

The speed difference is likely caused by the write cache being full. How is the CPU utilization during the test?

 

[costaandrea]

Dear all, thank you for all the suggestions. I think I finally solved the problem. I changed the switch to a nearly identical one but the transfer speed has increased substantially! Now I can transfer files at 80-90 MB/s and I can nearly saturate the gigabit lan using iPerf. I cannot fully understand why the old switch caused all these problems...however I trashed it...