Apparently going through 2 switches slows network transfers down considerably

[Doomer]

Transferring files from computer A to computer B via 2 switches. Both switches are gigabit. Router is also gigabit but transfers don't go through it. Transfer rates are between 11 and 22MBs. Moved computer B so that it's on the same switch as computer A and transfer rates jump to 80 to 90MBs. Not sure why there's such a big difference when going through a second switch but there is.

Anybody know why?

 

[drebo]

Probably a bad cable between the two switches.

 

[Lithium381]

What brand switches? 11mbps would point to a 100MB connection . . but that's a pretty big jump! a lot of other traffic on those switches? possible loop? lots of possibilities!

 

[skyking]

Probably a bad cable between the two switches.

that's what I get. Look at the lights, OP. The ports connecting at 1000 will show green on most switches. The ports connecting at 100 will be yellow or orange.

 

[xeledon20005]

perhaps bad switch?

 

[Doomer]

Both switches are Zyxel, one is a 24 port and the other a 16. Both are showing all 1gb connects. a 100mb connection would stick out like a sore thumb and I would investigate since I have nothing on the network that's 100mb. Guess it could b e a bad cable but I've had no other issues aside from this speed problem.

 

[drebo]

Probably a bad cable.

 

[Doomer]

Yep, that's my suspicion too. Hope it's not the one linking the two switches, that one will be a witch to replace.

 

[imagoon]

that one will be a witch to replace.

Murphy says it will be.

 

[thecoolnessrune]

Going to also vote bad cable. Almost all switches nowadays until you get into the really heavy stuff are non blocking, which means they should support full wire speed Layer 2 switching without any speed sacrifice, no matter how many ports are connected. The only other thing I can think of is if you have some other device on that switch that is spamming your destination computer and is cutting into your total bandwidth on that port.

 

[wsaenotsock]

Also most switches will indicate if the link state is 100mbit or Gbe with the color of the link-lights which makes finding the under performing adapter or cable easy.

 

[Eug]

Yeah prob bad cable.

I have consumer grade Gigabit switches and up to about 3-4 switches between point A to point B in some routes in my house and it still works fine for gigabit.

Yeah, my network topography is terrible, but that's what happens when you have to retrofit Gigabit into a house which originally had no networking at all.

 

[Doomer]

Ok, speed dropped again while transferring files so my 2 switch theroy and bad cable seems to be eliminated. I installed an Intel Pro 1000 in this box in the belief that it was superior to the on board Realtek. it may be but it also seems to be defective. I did notice that after moving the box I had to push in on the nic to get it to work at all. i thought nothing of it because I figured it creeped out of the slot during the move, even though it felt fully seated when I pushed on it. Anyway, after the push it started working. I then proceeded to transfer the files and at first, it started out at about 98MBs but then dropped to 11MBs after about 20 seconds. I've removed the Intel NIC and re enabled the on-board Realtek. So far so good but only time will tell. Just checked and speed has dropped to 50MBs. Guess I can live with that but not 11MBs.

Also, none of the cables are homemade.

 

[Eug]

Do you have hard drives or SSDs? Large sequential file transfers, or small files?

 

[Nothinman]

Ok, speed dropped again while transferring files so my 2 switch theroy and bad cable seems to be eliminated. I installed an Intel Pro 1000 in this box in the belief that it was superior to the on board Realtek. it may be but it also seems to be defective. I did notice that after moving the box I had to push in on the nic to get it to work at all. i thought nothing of it because I figured it creeped out of the slot during the move, even though it felt fully seated when I pushed on it. Anyway, after the push it started working. I then proceeded to transfer the files and at first, it started out at about 98MBs but then dropped to 11MBs after about 20 seconds. I've removed the Intel NIC and re enabled the on-board Realtek. So far so good but only time will tell. Just checked and speed has dropped to 50MBs. Guess I can live with that but not 11MBs.

Also, none of the cables are homemade.

As Eug implies, the disks in either location could be the problem. You can't do a pure network speed test with files coming from and going to hard disks. Have you tried something like iperf to test just the network side?

 

[dawks]

I always see highly variable network speeds, even with all gigabit equipment.. On Saturday I tried copying a file between my Windows Core i5-3570K at 4.2Ghz and my 8Core Mac Pro 2.8Ghz, both directly connected to a gigabit router, but the transfer only went at about 3-5megs/ sec. Then Sunday, I tried the same transfer with a different 10gig file, and it flew by at 55-60meg/sec. Nothing had changed, just the time. Happens one in 6-7 times roughly.

 

[Doomer]

Long weekend.

I did two thing over the weekend and the problem has disappeared. as it turns out, my 2 switch theory was wrong. I believe the Intel NIC is borderline bad. A couple of times I had to wiggle, monkey with it to get it to work so I took it out of the box and switched over to the onboard Realtek NIC. I also dumped Win 7 due to slooooow directory reads and loaded Server 2012. These two moves have cleared up all problems. I've been moving file around since yesterday it has been rock solid. Transfer rates are between 80 and 110 MBs. It has taken me over a week to get to this point and I've learned a few things along the way.

Thanks all.