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Author Topic: Strange data transfer speed issue through gigabit connection  (Read 14735 times)

vk

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Strange data transfer speed issue through gigabit connection
« on: April 13, 2010, 06:46:20 AM »

I'm running 1.08 with a pair of WD Caviar Green 1.5T as RAID1. Through fast ethernet connection (100Mbps) for large files I'm getting roughly 7MB/s actual data transfer speed for both reading and writing, not great but reasonable.

Lately I've got a new gigabit switch so I connected my DNS-323 to it, surprisingly for the same large file the reading speed has dropped to ~2MB/s, writing speed pretty much stays the same though. If I force my DNS-323 to run at 100Mbps (by applying 100Mbps under LAN settings) reading speed would come back to 7MB/s.

I'm getting the same result regardless the other end is gigabit or 100Mbps, both are laptops attached to the same gigabit switch. The switch itself works fine as I tested under a different environment with some desktops connected, the actual data transfer speed ranges from 30MB~60MB/s. I thought it might be a cable issue, but I've tried 2 separate cat5e cables with no luck. I've also tried to skip the switch by plugging my laptop into DNS-323 directly (using regular cable, apparently DNS-323 does auto sensing), however the speed stays low when I'm using laptop with gigabit port. I've also tried to reset my DNS-323 to factory default settings but the result stays the same.

This is really strange I have to say, anyone has any idea what's causing this issue?  Thanks.
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tedfroop

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Re: Strange data transfer speed issue through gigabit connection
« Reply #1 on: April 21, 2010, 07:38:36 PM »

Do you have jumbo frames enabled?  If you do your MTU may not match and could cause what you are seeing.
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DIR-655 - as access point
DGS-1005G x2
DGS-1008G
DNS-323 x2
DNS-325
2 Squeezeboxes

vk

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Re: Strange data transfer speed issue through gigabit connection
« Reply #2 on: April 22, 2010, 06:53:49 AM »

No it's off
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ECF

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Re: Strange data transfer speed issue through gigabit connection
« Reply #3 on: April 22, 2010, 08:17:24 AM »

Is it not connecting at GB automatically?

If you lock the DNS-323 to 100 and the Nic in your PC is not locked it may be failing over to half duplex lowering the transfer speed a little.
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Never forget that only dead fish swim with the stream

vk

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Re: Strange data transfer speed issue through gigabit connection
« Reply #4 on: April 23, 2010, 07:50:39 PM »

If i leave it as auto it does connect at 1000Mbps as shown by my switch, which is a d-link DGS-1008D, however the actual transfer speed is very low as I mentioned, so I had to force it to run at 100Mbps for now.
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AKFubar

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Re: Strange data transfer speed issue through gigabit connection
« Reply #5 on: April 24, 2010, 07:22:34 AM »

If you have any other devices on your network that are not gigbit rated it will cause your whole network to run at 100Mbps
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fordem

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Re: Strange data transfer speed issue through gigabit connection
« Reply #6 on: April 24, 2010, 07:51:48 AM »

If you have any other devices on your network that are not gigbit rated it will cause your whole network to run at 100Mbps

That is incorrect - you can connect 10/100 devices to your gigabit network switch without any slowdown - the network switch buffers the data.

There are probably hundreds of thousands of networks running servers on gigabit and desktops on 100mbit, in fact this is commonly done because it maximizes the throughput between the server(s) and the clients - you can have 10 clients running "full throttle" before the server connection becomes overloaded.
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RAID1 is for disk redundancy - NOT data backup - don't confuse the two.

vk

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Re: Strange data transfer speed issue through gigabit connection
« Reply #7 on: April 28, 2010, 10:27:53 PM »

Interesting enough, this appears as a Samba server configuration issue:

I've never thought SMB server is the one the blame, until the other day I realized I'm getting way better throughput from FTP comparing to SMB, which means it should not be a NIC driver issue. Around the same time I've noticed if I run Linux instead of Windows on the same PC I'm also getting way better throughput through SMB, which is really odd.

After putting on telnet I've noticed this line in Samba server configuration file (/etc/samba/smb.conf):
socket options = TCP_NODELAY SO_RCVBUF=65535 SO_SNDBUF=65535

Now that's interesting. When it comes to Samba performance tuning everywhere I look it recommends setting SO_RCVBUF/SO_SNDBUF to around 8192 to start with, why this little box needs 64K? So I changed it to 8K to see how it looks:
socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192

This change will not survive from a reboot because the firmware will recreate this file based on smb.default, so to make it take effect I had to kill all "smbd" processes, and re-launch "/usr/sbin/samba/smbd -D" at the end. As I expected, after making this change now I'm getting a healthy 9~10MB/s read/write speed from my Windows XP laptop with a 100Mbps NIC, it was only 2~3MB/s before I made the change (7~8MB/s if I force DNS-323 run at 100Mbps instead of gigabit).

On my laptop with gigabit connection the throughput has also been improved, but still a bit slow, I will tweak more to see if I can make it better.

Probably SMB server on DNS-323 was not optimized for Windows client? That is odd considering the main purpose of SMB is sharing for Windows.
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vk

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Re: Strange data transfer speed issue through gigabit connection
« Reply #8 on: April 30, 2010, 09:37:14 PM »

OK finally I've got this issue completely resolved!

For the slow transfer speed to my laptop with 100Mbps NIC, the issue is caused by Samba configuration setting on DNS-323 as I described in the previous post. After I modified that configuration file - now I made the change to smb.default and wrote it back to flash, so the change persists after reboot - writing to NAS does not change much, but reading from NAS now goes ~9MB/s comparing to ~3MB/s before I made the change.

For my laptop with gigabit NIC it's a totally different story though, it turns out it's Win7 to blame, not DNS-323. I've made a few changes on Win7 hoping to improve network throughput, including disable autotuning and turn off RDC (Google for details if you are interested), I do see some improvement but the speed is still under 100Mbps mark. Eventually I've found what's making it so slow on my low powered netbook - which is a HP mininote 2133 by the way - believe it or not it's "visual effect", after turning off "Animate controls and elements inside windows" under "Performance Options\Visual Effects" now I'm getting a stable 17~18MB/s reading speed from DNS-323, about 15MB/s for writing. Now I call it gigabit although not a very fast one  :D

The change I've made to Samba configuration file actually slightly slows down both NAS reading and writing speed for my gigabit NIC netbook, but only 0.5~1MB/s difference, which I can totally live with. I guess when D-Link tweaked Samba configuration to maximize network throughput they only had gigabit clients in mind, not mixed 100Mbps/1000Mbps environment, not a good idea I would say.
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lmnop64

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Re: Strange data transfer speed issue through gigabit connection
« Reply #9 on: April 26, 2014, 12:38:46 PM »

vk, I've made all the changes you suggested in this thread, and it still hasn't improved my speeds.  Does anyone else have any other suggestions to improve speed?
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ivan

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Re: Strange data transfer speed issue through gigabit connection
« Reply #10 on: April 28, 2014, 02:19:12 AM »

First up, what speeds are you getting?

Second, check cables?

Third, are you trying to connect using wireless?

Fourth, have you always had the problem or did it occur after you changed something on your network?

 
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