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Reproducible hang on network transfers

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It appears that, when transferring data from my desktop (ubuntu 9.04 desktop) to my new nas (ubuntu 9.04 server), it hangs for a short while every so often. When this happens, the transfer rate drops to 0 for 10-20 seconds, then picks up again. The same behavior manifests with smb and rsync transfers, and appears to happen mainly with larger files being transferred. I have attached two screenshots of the system monitor while an rsync transfer and a samba transfer are hanging up.

I have noticed that when this happens while drag+drop or copy+paste'ing through nautilus to the server share, the file operation will time out and wait for me to abort it. I will be testing this from my vista x64 desktop later today, but would appreciate it if anybody has any ideas on why this happens.

intel e6300 2.8ghz (wolfdale)
1x2gb ram
1x640gb wd green
4x1tb wd black in raid 5, xfs filesystem, default options from ubuntu installation
onboard pcie gigabit

intel q6600
2x2gb ram
2x1tb wd green in raid 1, ext3 filesystem
onboard pcie gigabit

cat6 cable all around
netgear gs105 switch


  • rsync copy to server.jpg
    rsync copy to server.jpg
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  • samba upload to server.jpg
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I don't have any real insight into your problem as I'm running just to stand still when it comes to all the nuances of file transfers. But here's my braindump on this.

1. I notice a very small CPU "peak" on one or more cores before each drop in throughput. Could some other task on the client be getting priority?

2. Your write speed seems a little low for your excellent setup. From my client (XPSP3x86, 2GB RAM, E8400 3GHz, WD7500AAKS, PCIE Gb NIC) to my server (Ubuntu904x64, 4GB RAM, E1400 2GHz, 3xST3500410AS Linux-RAID10, PCIE Gb NIC) I see 70-80MB/s write speed. Perhaps your wd green array in the client is a bottleneck? Maybe it's spinning down if idling while files are written from RAM to network? Just assumptions.

3. Jumbo frames? If you're using them, try disabling them on both ends or changing packet size. If you're not using them you could give them a try. Wouldn't fix your problem but might give you an increase in throughput.

The Vista test might well cast new light on your issue.

Good luck,

Ok, I just transferred a 7.56GB folder to and from my nas server from my vista desktop over 3 hop connection (vista pc -> netgear gs105 -> netgear gs108 -> netgear gs105 -> nas server) and, with a stopwatch app, timed it to roughly 133 seconds with no real slumps in the transfer (aside from the momentary bottoming out spike where it started the next file copying), and roughly 148 seconds to transfer back, which works out to ~52-58MB/s. It seems that it may just be a problem with my ubuntu desktop.

I will start a new thread for my vista iperf testing...
I recall in the past having trouble with SAMBA on Ubuntu Desktop (7.10). From what I recall I had to make sure I mounted the drive as CIFS with certain settings. It has been quite a while since I used Ubuntu Desktop so not exactly sure. Along with that remember that SAMBA is basically an attempt to copy how windows transfers files. When used on the server side SAMBA seems to work well but I am unsure if the SAMBA client has been optimized for performance. Along with that Nautilus might not be the best way to try the file copy. Try using the command line to copy a file and see if your results are similar.


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