About Bandwidth

[pakigang]

There are network cards that do 1Gbit & even 4Gbit & i think even 8 Gbit has been introduced for web servers.

My question is that 1 Gbit = 1000/8 = 125 MB/s apporximate, can be accomplished by pc when you HDD is ATA 150 which is also not used completely??

 

[TuxDave]

Originally posted by: pakigang
There are network cards that do 1Gbit & even 4Gbit & i think even 8 Gbit has been introduced for web servers.

My question is that 1 Gbit = 1000/8 = 125 MB/s apporximate, can be accomplished by pc when you HDD is ATA 150 which is also not used completely??

Translation: Why is it so hard to get 1Gb/sec ethernet when we have harddrives that can easily accomplish that?

My answer, because it's a whole different playing field. I'm sure you have read ratings on the maximum length of SATA cables and I'm assuming that number isn't very large. The longer the cable, the greater the amount of reflections and distortion. I doubt you'll get 150MB/sec if you have a SATA stretched out 20ft or so. Maybe I'm wrong, someone can check me on that. But longer cables have more reflections and a worse frequency response that'll make signal recovery and transmission harder.

 

[AbsolutDealage]

Originally posted by: TuxDave
Translation: Why is it so hard to get 1Gb/sec ethernet when we have harddrives that can easily accomplish that?

I think what he is getting at here is the opposite:

Translation: Why can we fill a 125MB/sec (500MB/sec, 1000MB/sec) ethernet pipe when we cannot even fill a 150 MB/sec pipe for a hard disk?

 

[imported_Hamzter]

Well that computer could be using a RAID array, or it could just be that it can sustain that transfer rate for a small ammount of time because the information is stored in the RAM.

 

[Homerboy]

Well Ive never heard of anything over 1gig for PC/server network card.
Now if you're talking routers and such, thats a different story. Of course we can fill 1/4/8/10Gsec on backbone routers and such, you have 100s, 1000s, 10000s of people hitting them at the same time.

 

[TuxDave]

Originally posted by: AbsolutDealage

Originally posted by: TuxDave
Translation: Why is it so hard to get 1Gb/sec ethernet when we have harddrives that can easily accomplish that?

I think what he is getting at here is the opposite:

Translation: Why can we fill a 125MB/sec (500MB/sec, 1000MB/sec) ethernet pipe when we cannot even fill a 150 MB/sec pipe for a hard disk?

Haha.... perhaps that's right. My brain exploded twice while trying to parse his original question.

 

[Calin]

Those very fast network connections are used for two reasons (I can think of). One would be the burst transfer rates for data from memory (transferring data from memory to the network card over PCI is limited to something like 133 MB/s, so it could saturate the network connection if nothing else happen (like another network card, a hard drive or something). The other reason is to get rid faster of processes that want to transmit some data - if you can send the data 10 times faster, you will have fewer processes in memory, so more memory available.
The reason some chipsets move the network card away from the PCI bus would be that, with both hard drive controllers and network cards on the PCI bus, a download would be unable to work at the speed of the network card (the PCI bandwidth would be saturated by the network card, leaving the destination hard disk "gasping for breath".

 

[pakigang]

What i'm trying to say that the average r/w speed of hardrives is around 50/40 MBytes/s with max upto 70.

It seems that gigabit ethernet cannot be used to full potential, just half on the max on a desktop pc, if not then how is it accomplished??

 

[Calin]

Yes, a single (or even two) hard drives cannot saturate a gigabit ethernet. However, the reason to introduce the gigabit ethernet was not to surpass a hard drive transfer speed or capabilities, but to: improve application responsiveness when the application is run from a remote file system (think computers without hard drives, and file systems enclosed in server's RAM. Also, some database servers are perfectly capable to fill the gigabit ethernet.

The reason for introduction of gigabit ethernet was not as much to reduce the time to transfer a file from 10 minutes to 1 minute, but to reduce the time of transfer from a tenth of a second to a hundredth of a second.

 

[Concillian]

Originally posted by: pakigang
It seems that gigabit ethernet cannot be used to full potential, just half on the max on a desktop pc, if not then how is it accomplished??

You're correct, it cannot be used to full potential on a desktop PC.

You do not have to use something to full potential for it to be beneficial.

When you use something to full potential suddenly it transforms into a bottleneck.

 

[ahurtt]

Originally posted by: Concillian

Originally posted by: pakigang
It seems that gigabit ethernet cannot be used to full potential, just half on the max on a desktop pc, if not then how is it accomplished??

You're correct, it cannot be used to full potential on a desktop PC.

You do not have to use something to full potential for it to be beneficial.

When you use something to full potential suddenly it transforms into a bottleneck.

It cannot be used to full potential on 1 desktop pc. But a network is a bunch of PC's. You have to divide up the available bandwidth between all of them. So say if you have 1 network connection capable of transferring 100 MB / sec and 2 PC's each capable of receiving 75 MB / sec. Suddenly, the pipe is not big enough for both of these PC's to saturate their max transfer recieve rates at the same time, but it is too big for either of them to fill individually. That is the reason ethernet needs to be faster than any 1 pc can use. Because you are networking many PC's. When you are talking about a machine that has an 8Gbit ethernet interface, you are not talking about an average desktop PC. You are talking about a heavy duty server or cluster serving up services to a network. . .like the internet.

 

[Calin]

A switch (as opposed to a hub) in a network will give to each computer the available bandwidth of the network (in the best case). The worst case (when every computer wants to transmit/receive to a certain other computer will share the total bandwidth of that certain computer to all the others that request it. And in some cases there can be network connections just between two computers (no switch, no hub)

 

[ahurtt]

Originally posted by: Calin
A switch (as opposed to a hub) in a network will give to each computer the available bandwidth of the network (in the best case). The worst case (when every computer wants to transmit/receive to a certain other computer will share the total bandwidth of that certain computer to all the others that request it. And in some cases there can be network connections just between two computers (no switch, no hub)

And further to this point, not every device that has a network interface of some sort also contains a hard drive. Often dedicated switches, hubs, and routers are dedicated pieces of hardware that exist solely to handle networks and their traffic and contain no hard drives or other moving parts.

 

[imported_Phil]

Originally posted by: ahurtt

Originally posted by: Calin
A switch (as opposed to a hub) in a network will give to each computer the available bandwidth of the network (in the best case). The worst case (when every computer wants to transmit/receive to a certain other computer will share the total bandwidth of that certain computer to all the others that request it. And in some cases there can be network connections just between two computers (no switch, no hub)

And further to this point, not every device that has a network interface of some sort also contains a hard drive. Often dedicated switches, hubs, and routers are dedicated pieces of hardware that exist solely to handle networks and their traffic and contain no hard drives or other moving parts.

Not forgetting, of course, that a decent RAID array on a server would push 125Mb/sec easily.

 

[gwag]

I have a friend who sets up archive and data storage primarily for design house often using 40+fibre channel, or scsi disc raids they can have 500MB/s transfer rates ungodly costs, robotic tape loaders etc. I think his co. did a 17TB install a few months ago. A lot of these jobs will spend $50,000- 100,000? on this technology and the majority of there machines don?t even have GB Ethernet (mostly older Macs) but I am guessing there buying for the future. He has amassed an army of older 9-18G fibre channel drives from upgrades one day I will have to get a controller and mess with em.

 

[sharkeeper]

Not forgetting, of course, that a decent RAID array on a server would push 125Mb/sec easily.

Without even breathing let alone breaking a sweat.

10Gb/S interfaces are around and 100 and 1000Gb/S interfaces are about to emerge.

Interfaces were designed to eliminate bottlenecks, not for single users to have seemingly unlimited bandwidth. For those blessed with ability to have the latter, admittingly, it's nice.

 

[imported_Kensai]

I wouldn't mind having a 1Gb/s connection. Would help me download better. Also, everything depends on the barebone and specification. The specifictation of internet that we use today was developed over 10 years ago. That's why we're hitting such a bottleneck. I believe there's a chain of universities in the states that have set up a small version of the Internet spec 2.

 

[ndolf]

Originally posted by: Kensai
I wouldn't mind having a 1Gb/s connection. Would help me download better. Also, everything depends on the barebone and specification. The specifictation of internet that we use today was developed over 10 years ago. That's why we're hitting such a bottleneck. I believe there's a chain of universities in the states that have set up a small version of the Internet spec 2.

if u are using 1Gb/s, u prob need to finance it like ur car