What might limit data transfer rate to NAS?

Question

I have two NAS (Buffalo Linkstation Pro, WD MyBook World), which are connected to 2 PCs with a Gigabit LAN connection. All devices are in "Gigabit mode", meaning all show that their connection speed is really 1 GBit. But the transfer rates to and from the NAS drives are very low, on average 5 MByte/sec, copying large files with several GByte in size.

Looking at the spec of the Buffalo drive, it should do up to 30 MBytes/sec. Of course, this is probably a best case scenario, but I think more than what I have right now should be possible.

Copying files between the two PCs is much faster, about 25 MBytes/sec.

What could limit the data transfer? What can I do to increase it?

Solution

The WD MyBook World is CPU-bound or disk-controller-bound. If you do an online search for the throughput of the first versions of MBW, you will find that 5MB/s is quite common. There is nothing you can do about this.

Comments

[Holgerwa]

I had Jumbo Frames enabled before, but checked again to make sure: PCs, NAS and switches support Jumbo Frames, on PCs and NAS that's enabled. I guess the switches just support it since there is no setup.

[Holgerwa]

I copy a large file (10GB) from a PC's local disk to one NAS. Transfer: 4,5MB/sec; CPU utilization: 15%; Netzwork traffic: 4%. Only NAS, PC and switches are on, second PC and second NAS are off to make sure they are not doing anything on the network. But that's the issue: Why is not more of the available resources used?

[juanefren]

What kind of harddisk(s) are in the NAS you are copying to? ... and what is the model no. of the NAS?

[Holgerwa]

The Buffalo NAS has a Samsung HD103UJ, 1TB, 7200rpm. Sounds not too bad, it should not be the bottleneck.

[Chris W. Rea]

Cases in point: discuss.extremetech.com/forums/2/1004412081/ShowThread.aspx and tomshardware.com/forum/…

[Holgerwa]

Wow, that's an eye opener. So basically, WD is selling junk but putting a GBit sticker on it so people won't realize how bad it is until after the purchase. That doesn't produce returning customers...

[Mat]

"connected to 2 PCs with a Gigabit LAN connection. All devices are in "Gigabit mode", meaning all show that their connection speed is really 1 GBit"

[Arjan]

@Mat, that's about the network, not about how the disk is connected to the NAS.

[Mat]

Both the models mentionned have external USB 2.0 ports (and an internal drive). USB 2.0 transfer rates are well above 5Mo/s.

[Arjan]

Still then, @Mat, I feel this might help future visitors who're looking for "What might limit data transfer rate to NAS?".