What LAN speeds can I expect?
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Posted by Stephanie on March 5, 2008, 12:15 am
Please log in for more thread options suspended ceiling and into the walls. All connections use quality hardware. The gigabit switch is a LinkSys SR2024: <http://tinyurl.com/39s8xr>
The computers are 1-year-old Dell desktops running a mix of Win XP and 2K. These have Intel brand gigabit NICs installed. There is nothing between computers on the LAN except the SR2024. When copying a test file between computers, we're seeing 10-12 megabytes/second. This isn't anywhere near what I was expecting. I realize that 1 gigabit speeds are only theoretical and reserved for only those optimized systems with the fastest busses and hard drives, but I think my numbers are a tad low. What speeds can we expect? What is slowing down this new network? Thanks. | |||||||||||||||||||||||||
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Posted by Bob Willard on March 5, 2008, 7:17 am
Please log in for more thread options > We just upgraded the office network, pulling new cat-5e cable over the
> suspended ceiling and into the walls. All connections use quality hardware. > The gigabit switch is a LinkSys SR2024: > > <http://tinyurl.com/39s8xr> > > The computers are 1-year-old Dell desktops running a mix of Win XP and 2K. > These have Intel brand gigabit NICs installed. > > There is nothing between computers on the LAN except the SR2024. > > When copying a test file between computers, we're seeing 10-12 > megabytes/second. This isn't anywhere near what I was expecting. I realize > that 1 gigabit speeds are only theoretical and reserved for only those > optimized systems with the fastest busses and hard drives, but I think my > numbers are a tad low. > > What speeds can we expect? What is slowing down this new network? > > Thanks. > First, make sure you are using a single large file, rather than a folder full of small files, to minimize the effect of per-file overhead in the filesystem. Also, make sure the file is contiguous, although a newly- created file on a HD with lots of empty space almost surely is. And, make sure the file is large enough that you can measure transfer time with a watch (and then hand-calculate the STR, or Sustained Transfer Rate); some apps are kinda sloppy about reporting STR. Next, do your testing with only one OS, either XP or W2K; I've seen great differences between mixed and pure OS results. {If achieving maximum STR is really important, you should plan on replacing all W2K boxes with XP boxes, and adding RAM. Did I mention Vista? Not.} Next, note that there are four cases, and potentially four different STRs: A pushing a file to B, A pulling a file from B, B pushing to A, and B pulling a file from A. Next, repeat the measurements several times, and use the highest STR as the basis for comparison when you try something different. Next, eliminate the switch by connecting a pair of your fastest XP PCs with a crossover cable in place of the switch. Repeat the STR measurements to see the "insertion loss" caused by the switch. I have no clue about that particular switch, but it has to buffer at least a part of every incoming packet to decide how to handle that packet, and that delays packet delivery, even without congestion effects. Finally, experiment with tuning the network drivers. Most importantly, pick a size for jumbo frames and use the same size for your entire LAN. Increasing the number of Xmt and Rcv transmit descriptors might help, but they chew up RAM on the PCs. I suspect that you want both Xmt and Rcv flow control turned on, but you might experiment with that. Good luck. And please report back what you find and what you achieve. -- Cheers, Bob | |||||||||||||||||||||||||
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Posted by Robert Redelmeier on March 5, 2008, 8:08 am
Please log in for more thread options > These have Intel brand gigabit NICs installed.
In PCI or PCI-e slots? PCI (no e) bursts at 133 MB/s but has short burst and high setup overhead. 30-40 MB/s is common. > When copying a test file between computers, we're seeing 10-12
> megabytes/second. This isn't anywhere near what I was expecting. These sound like 100baseTX speeds. Are you sure your cabling is good? (ie not homemade) Do not use files for transfer, the disk controller also sits on the PCI bus! Try `ttcp` or other memory-based source/sink. -- Robert | |||||||||||||||||||||||||
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Posted by Jeff Liebermann on March 5, 2008, 11:18 am
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>We just upgraded the office network, pulling new cat-5e cable over the
>suspended ceiling and into the walls. All connections use quality hardware. >The gigabit switch is a LinkSys SR2024: > ><http://tinyurl.com/39s8xr> > >The computers are 1-year-old Dell desktops running a mix of Win XP and 2K. >These have Intel brand gigabit NICs installed. > >There is nothing between computers on the LAN except the SR2024. > >When copying a test file between computers, we're seeing 10-12 >megabytes/second. This isn't anywhere near what I was expecting. I realize >that 1 gigabit speeds are only theoretical and reserved for only those >optimized systems with the fastest busses and hard drives, but I think my >numbers are a tad low. > >What speeds can we expect? What is slowing down this new network? Your question has nothing to do with wireless. Why post to a wireless newsgroup? Are you using Vista? The current version is known to have a file copy performance problem. One of many solutions: <http://www.ocmodshop.com/ocmodshop.aspx?a=900>
while waiting for Vista SP1.
For proper benchmarking, go thee unto: <http://dast.nlanr.net/Projects/Iperf/>
and docs at:
<http://dast.nlanr.net/Projects/Iperf/iperfdocs_1.7.0.html>
Download IPerf 1.7.0. Designate one machine as the "server" an run:
iperf -s on it. Note it's IP address. You'll need it. The other machines will be designated "clients". On them, run: iperf -c ip_address_of_server I'm not at my palatial office at this time and do not have a gigabit LAN handy to give you my numbers. As I recall, I was getting about 40Mbits/sec between Linux and XP boxes, with no optimization or tweaking, through a Linksys SD2005 switch. To do better, I had to tweak IP parameters per: <http://www.psc.edu/networking/projects/tcptune/>
You're not the first person to blunder into the optimization problem. See this review of a gigabit ethernet switch, where the author didn't optimize the test machines and got similar results to yours: <http://www.extremeoverclocking.com/reviews/networking/Linksys_EG008W_3.html>
I found some results for just the gigabit ethernet cards and Iperf at: <http://www.digit-life.com/articles2/gigeth32bit/gig-eth-32bit-2.html>
Note the differences in performance with jumbo packets and a large
MTU. The first test you should make is with just the two machines, using a crossover ethernet cable. Zero switching hardware and CAT5 spaghetti in the loop. Just the two machines. If one of your machines is slothish, buggish, defectish, or pre-occupied with doing updates, this will show the problem. Once you get reasonable numbers for just the test machine, add in the Linksys SR2024 switch and watch them drop slightly. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 | |||||||||||||||||||||||||
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Posted by Jeff Liebermann on March 8, 2008, 7:33 pm
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>For proper benchmarking, go thee unto:
(...)
><http://dast.nlanr.net/Projects/Iperf/> >and docs at: ><http://dast.nlanr.net/Projects/Iperf/iperfdocs_1.7.0.html> >Download IPerf 1.7.0. Designate one machine as the "server" an run: > iperf -s >on it. Note it's IP address. You'll need it. > >The other machines will be designated "clients". On them, run: > iperf -c ip_address_of_server I ended up doing a weekend service call (grrrr...) and took a few minutes to benchmark a gigabit ethernet system. The client and server are both Dell Optiplex 755 machines (2.6GHz Core2Duo, 1333Mhz FSB, 2GB DDR2, SATA-II HD, etc). Both running XP SP2 with the lastest band-aids. Very nice fast machines (I want one). The switch is a bottom of the line DLink DGS-2205 5 port swtich. On the server, I ran: | iperf -s -M 100000 -w 64K -l 24K or: Packet size = 1514 bytes Window size = 64KBytes Buffer size = 24Kbytes On the client, I ran: | C:\>iperf -c 192.168.1.100 -M 100000 -w 64K -l 24K
| ------------------------------------------------------------
| Client connecting to 192.168.1.100, TCP port 5001 | TCP window size: 64.0 KByte | ------------------------------------------------------------ | [1908] local 192.168.1.101 port 2362 connected with 192.168.1.100 port 5001 | [ ID] Interval Transfer Bandwidth | [1908] 0.0-10.0 sec 1.09 GBytes 934 Mbits/sec | [1908] 0.0-10.0 sec 1.06 GBytes 905 Mbits/sec | [1908] 0.0-10.0 sec 1.08 GBytes 929 Mbits/sec This is almost wire speed and about as good as TCP gets. UDP would be slightly faster. I then ran it again using the default iperf parameters: | C:\>iperf -c 192.168.1.100
| ------------------------------------------------------------
| Client connecting to 192.168.1.100, TCP port 5001 | TCP window size: 8.00 KByte (default) | ------------------------------------------------------------ | [1908] local 192.168.1.101 port 2378 connected with 192.168.1.100 port 5001 | [ ID] Interval Transfer Bandwidth | [1908] 0.0-10.0 sec 639 MBytes 535 Mbits/sec Yech. That's about half the rated speed and rather insipid. Big buffers are helpful. I didn't have time to try jumbo packets. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 | |||||||||||||||||||||||||
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