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[Robocub]

I'm having a problem of slower file transfer speeds when copying files from HD1 to HD1 on my DNS-323. I have my HD setup as 2 separate drives (jbod). Speeds max out at about 3-4MB/sec. However if I copy files to my iMac's Desktop, I get transfer speeds ranging around 14-18MB/sec. I have Jumbo Frames enabled and MTU at 9000 on both DNS and my iMac. Shouldn't HD1 to HD2 speeds be faster since it's on the same bus?

[fordem]

No - you're actually copying from the DNS-323 across the network to your Mac and then across the network a second time to the DNS-323, and not "across the same bus" as you think.

By the way - that disk configuration is considered to be "standard volumes" by D-Link - JBOD is something else altogether.

[Robocub]

Thanks Foredom. I understand what you'r saying but it still doesn't explain why the transfer is significantly slower than from the DNS to my Desktop.

[hilaireg]

In order for Jumbo Framing to function correctly, the entire network end-to-end must support Jumbo Framing.  What network switch are you using? 

Cheers,

[Robocub]

My network consists of the DNS-323 and an iMac C2D (with gigabit nic). Connecting the DNS and iMac is a Netgear GS605. But as I said, DNS to iMac (and vice versa) file copying is on average 14-19MB/sec, as is expected. Copying files from one HD to another in the DNS only averages at 3-4MB/sec.

[hilaireg]

Had a quick look at the specifications on the GS605; seems to indicate that it supports Jumbo Framing (http://www.netgear.com/Products/Switches/DesktopSwitches/GS605.aspx?detail=Specifications) but it isn't clear if the feature needs to be enabled - I suspect it's inherently "on".

As 'fordem' indicated, you're not actually performing a direct disk-to-disk copy.  If you are using your iMac to copy the files from volume_1 to volume_2 for example, the data would be transmitted down from volume_1 to the iMac and then from the iMac to volume_2.

Cheers,

[Robocub]

hilaireg, I totally understand what your saying. I guess what I find confusing is if file copying from DNS to iMac is ~19MB/sec, then why would (HD1 to iMac, iMac to HD2) be so significantly slower at ~4MB/sec? Hmm, I guess I'll just have to live with it. Thanks all for the helpful explanations. Much appreciated.

[hilaireg]

When u have a moment, monitor the throughput on a file copy session from the DNS to the iMac.  Once the copy is completed, copy the same files to the other volume and monitor the throughput.

Post the results of your observations to see if anyone from D-Link Engineering can shed some light.

Cheers,

[Robocub]

Copying a 733MB file from DNS Volume_2 to iMac Desktop = transfer speed ~40MB/sec.
Copying a 733MB file from iMac Desktop to DNS Volume_2 = transfer speed ~20MB/sec.

Copying a 733MB file from DNS Volume_1 to iMac Desktop = transfer speed ~40MB/sec.
Copying a 733MB file from iMac Desktop to DNS Volume_1 = transfer speed ~20MB/sec.

[gunrunnerjohn]

I'd like to know how you get 40mbyte/sec transfers.

[Robocub]

~40MB/sec is the approx max throughput I've seen. I hovers anywhere between 30-40MB/sec for the file transfer I did mentioned in previous messages on this thread.

I have Jumbo frames on and MTU set at 9000 for both my DNS-323 and my iMac network settings. I tried playing with MTU sizes in 1000 increments, but I didn't notice any difference so I just left it at 9000. ALso it's important to have a gigabit switch that supports jumbo frames. I had a Netgear GS605 v1 which I discovered didn't support jumbo frames. So them I bought a GS605 v2 which does support jumbo frames. Nothing to setup, it's automatic.

I'd like to know how you get 40mbyte/sec transfers.

[gunrunnerjohn]

I have all of the above, but I have never seen anything approaching 40mbyte transfers.   I see in the mid 20's at the highest.  All of my equipment supports jumbo frames and since this system is a 2.8ghz quad-core, I doubt it's system speed.

Who knows...

[fordem]

In a discussion on throughput in what is essentially a disk-to-disk transfer, why is the focus on processing power - would a 2.8GHz quad-core allow disk write speed significantly greater than a 3.0GHz HT processor?

Should we not focus a little more closely on things that perhaps play a greater part in the activity at hand - perhaps the disk subsystem?

Personally - I've never seen 40Mbyte/sec transfers either, but I have seen 35Mbyte/sec with the "aforementioned" 3.0GHz based system, writing to a pair of 250GB disks in a RAID1 configuration, and I've also seen significant performance degradation on the same system after switching to three 250GB disks in a RAID5 configuration.

[Robocub]

Hi all, I have attached a screen shot of a 1.33GB sized AVI movie file I downloaded from my DNS volume_2 to my iMac's Desktop. I grabbed the screenshot just as the transfer speed hit 37.1MB/sec and took 36 seconds to complete the download, someone can do the math. I've seen it hit 41 but not sustained. It fluctuated up and down from that point but hovered around 35MB/sec. I tried to grab it at a high point. Now whether this is a true accurate gauge of true throughput, I cannot say. But that is what it displayed.

[gunrunnerjohn]

In a discussion on throughput in what is essentially a disk-to-disk transfer, why is the focus on processing power - would a 2.8GHz quad-core allow disk write speed significantly greater than a 3.0GHz HT processor?

Should we not focus a little more closely on things that perhaps play a greater part in the activity at hand - perhaps the disk subsystem?

Once again you apparently miss my point.  I was only trying to point out that nothing in my system should be limiting the speeds from the NAS.  I have gigabit with jumbo frames and a sufficiently fast processor writing to a 10k RPM Raptor drive.  I'm just trying to figure out why some folks get the faster transfer speeds being reported here.