why are local file transfers slower than 1Gbps /100Mbps

Question

I have 2 computers both with 1Gbps ethernet cars (PCI) and are connected to a 1Gbps capable Switch with Cat 5e ethernet cable. Why are file transfers so much slower than 100Mbps let alone 1Gbps. (note I'm not asking about anything to do with the internet) My switch is connected to a router which is at least 100Mps ethernet speed. So would the file go from

one computer -> switch -> router -> switch -> other computer

or simply

one computer -> switch -> other computer?

Solution 1

For the first part of your question:

You are limited to the hard drive speed of your SLOWEST drive in the transfer. Your mega fast switch and NIC and badass new PC with the 15,000 rpm drives can only send data to the 10 yr old laptop as fast as it can write it to a drive.

For the second part:

It depends on how the devices are connected. If (as I suspect) your computers are on the same ip schema, and the switch has its uplink port into the router, then the router is not involved. The router would only be included if it were two pcs on different ip schemas or subnets.

Solution 2

There are quite a number of reasons this could happen. Not all hard drives are created equal and you would be lucky to get 1Gbps from a consumer drive except under ideal conditions such as reading a single, large file with no fragmentation. Lots of smaller files have added overhead, and fragmentation increases access time. Also, unless you have very expensive components, both the SATA and NIC require interaction from the CPU, so other programs will slows things down. If you are running anti-virus software this may also be checking the data as it is accessed further slowing down the process. Last, and this is probably least important, Cat6 is recommended for GigE.

Solution 3

One other minor point: Many routers and switches say that they're GigE capable, but are really just referring to the interface. Often the data transfer between ports will be limited to a much lower speed due to hardware/software reasons.

Solution 4

Keep in mind, Windows Vista/7 reports transfer speeds in Megabytes per second (MBps) not Megabits per second (Mbps). Link speeds are rated in bits not bytes per second. 1000 Mbps is equivalent to about 125 MBps...but, many other factors (includding PCI bus limitations/HDD speeds/cable quality) reduce the 1Gbps throughput to something closer to 400 Mbps. 50-75 MBps transfer rates are not uncommon....on my 7200 RPM drive, I'm only getting 20 MBps.

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Comments

[Tamara Wijsman]

Have you thought about the speed of the hard drive? Try a local copy on the computer and see how fast that goes. I think this question would fit better on ServerFault as it is a network question.

[Jonathan.]

ok, so is there a way I can take the hard drive out of the equation, like a program that just sends junk over the network to test the speed of the network.

[Joe_Rose]

Qcheck: ixchariot.com/products/datasheets/qcheck.html is a good utility to use to test local network speeds.

[Tamara Wijsman]

See serverfault.com/questions/5111/… for other alternatives.

[Joe_Rose]

Nice find, @TomWij.

[Jonathan.]

one of my harddrives in apparently 3Gbps and the other is 1.5 Gbps and transferring a file from one to another is about 0.4Gbps and copying files from one location to another on the same harddrive is also about 0.4 Gbps. So I guess know I have to look at the speed of the SATA on my motherboard?

[Joe_Rose]

@Jonathan - that would be a good place to start. Also make sure those speeds you quoted are SUSTAINED transfer and not BURST transfer.

[Tamara Wijsman]

hdtune.com can help you with this.

[Joe_Rose]

@TomWij - Good call as always.

[Montag451]

3 Gbps and 1,5 Gbps are just your harddrives interface controller speeds. Your disks mechanical parts (the heads which read data from the disk surface) do not read at the same speed as the disk's interface speed. Nowadays the best customer harddrives can just top at 120 MB/s which translates to nearly 1 Gbps. Don't forget that those top performers aren't ordinary cheap HDDs that you'll have on your household PC (or on an office PC). Those HDDs are the ones like WD's Velociraptor etc. This a good and old read for all things HDD : storagereview.com/hard_disk_drive_reference_guide

[Joe_Rose]

Nice, @Deniz! I'll remember that link.