Slowdown on cheap gigabit switches

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Andy
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Slowdown on cheap gigabit switches

Post by Andy »

I have a fairly cheap Plexus gigabit switch on my home network, and last night while transferring a 38gb file (backup image) to my desktop from my server, I found it running at 45MB/s, which is fairly good considering the drive in the server isn't amazingly fast. However, after about 2-3 minutes, the speed dropped to 6MB/s solid, and never went back up, even after restarting the transfer. If I leave the transfer stopped for about 5 minutes, and restart it, it is again back at 45MB/s for a few minutes, then drops to 6MB/s again.

I tested to make sure this was a switch issue by using a crossover cable between the server and my desktop pc, and it stuck at a solid 45MB/s for the entire transfer that way. I tested again with the switch, and the same slowdown occurred. Now, I spoke to mrpijey and he said its likely that because its a cheap switch it can only cope with gigabit for bursting, not continuously (and his advice hasn't failed me before, just want more opinions/experiences). Now I don't know about you but surely this is false advertising and shouldn't be allowed to be sold as a gigabit switch if its not capable of handling it continuously?

Has anyone else had this same issue before with cheap switches? I'm debating whether to send it back or not if this is an issue that shouldn't be happening. Obviously if its a known issue and happens with all cheap switches, sending it back would be pointless (if the RMA is even accepted at all).

Cheers all.

leonbollerup
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Re: Slowdown on cheap gigabit switches

Post by leonbollerup »

Hi,

We had similar issues with some switches at the office, mainly with preforming large-scale .vhd backups from our hyper-v servers - now everything is replaced with 3com and at home i use Apple Airport Extreme.

//Leon

Ps.
I was told by our provider, that our switches, would slowdown on over heating - did yours get warm ?

Andy
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Re: Slowdown on cheap gigabit switches

Post by Andy »

Thanks Leon. No it doesn't feel warm to the touch (metal case too). Its not even luke warm, just ambient warm.

Whistler_fan
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Re: Slowdown on cheap gigabit switches

Post by Whistler_fan »

Sometimes they use the same size of memory in the 1000Mbps switches (to act as a buffer) as a 100 Mbps, So when you're going to transfer a big file the buffer gets overflowed and because it cant buffer anything anymore the transfer speed droppes. Also they use sometimes the same type of hardware of 100Mbps switches but with another NIC controller but with the same internal CPU so that can also be overloaded (mostly you can feel that the switch is warmer then usual)

This is why mostly those cheaper switches are cheap.

I got the same issue a while ago and my teacher told me this.

oasiz
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Re: Slowdown on cheap gigabit switches

Post by oasiz »

Yes indeed. Cheap switches tend to do that.
My friend just bought a d-link gigabit switch that hangs when there are many devices connected.
What he found out is that looking from the datasheets the switching capacity was way too low for the purposes.

Have a look at this for example: http://h20195.www2.hp.com/v2/GetPDF.asp ... 131EEE.pdf (EDIT: I have the 8-port version, forgot to add!)
This is the switch that I bought for my usage. I constantly do heavy transferring, having a 110/5 internet + gigabit link to my server that basically holds 98% of my stuff. I still get stable 48-65mb/s.
The only time it lowers is when a slower disk is accessed (not the routers fault). It has never crashed, neither overloaded. I strongly recommend something like this.
16G capacity (=full duplex on all ports and should take it).
Most 'plastic fantastic' -boxes may look neat, but I have mostly found them very under performing, Where some consumer networking solutions are a complete joke.

Also check the usual cables and stuff to see if there is some loss occurring. But I believe that you are having some overload due to many devices performing at the same time. If you have the money to shell for this box then I highly recommend getting it. You will not regret it.
</sales pitch>
Last edited by oasiz on Fri Jun 05, 2009 11:52 pm, edited 1 time in total.

Gnome
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Re: Slowdown on cheap gigabit switches

Post by Gnome »

How much did you pay for the hub. And didn't you say to me gigabit was pointless?

Andy
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Re: Slowdown on cheap gigabit switches

Post by Andy »

£36 or so from eBuyer, their cheapest switch (and it shows obviously). Gigabit isn't pointless no, I don't think I ever said that.

Gnome
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Re: Slowdown on cheap gigabit switches

Post by Gnome »

Meh, both of mine were around £150 - £170. One 5-port one 8-port, highest i've hit is 70mbp/s

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