Tuning a gigabit LAN

[heyvern]

I recently changed over our small graphic arts office from fast ethernet to gigabit ethernet as we had done some renovating and I was able easily run new cat5e cabling. We were on a tight budget so I bought some lower end hardware that included 2 Trendnet 8 port gigabit non-managed switches and all gigabit NIC's based on the realtek 8169 chips. I was hoping for at least a small performance increase in network throughput but overall that hasn't happened. In a nutshell here is what seems to be happening. Using windows file manager Large and medium size file transfers are about 10% faster, however small file transfers (1-5kb) have slowed to a snails pace (painfully so when backing up a 100,000+ 2-3 kb png icon files). 10-15 times longer transfer times than at 100mbps. After reading a ton of posts about gb lans it seems that a lot of tweaking and tuning is needed to get the best overall performance. I have searched for a magic all inclusive chart with tweak recommendations but would settle for any suggestions that might help especially with the small file transfer speeds. I have all the latest drivers for the NIC's and have tried experimenting with Jumbo frames and various Tx and Rx window sizes none of which seem to change much. Most testing has been just drag and drop but using a command line app such as pcattcp shows the same results. Here is an overview of my current setup.

12 1.8 to 3ghz p2p workgroup PC's connected to each other via the 2 8 port gigabit switches. All machines have performance subsystems including RAID 0 Ultra160 or 320 multi disk SCSI Arrays. Max cable length on any segment is 10 meters, star topology. No network printers. No router or internet. OS's include Win2KPro, WinXPPro, Win2K server and Win98. Protocols include TCP/IP, IPX/SPX and NetBeui (required for some proprietary software)
Any help or suggestions on what reg tweaks or NIC settings to get the most reasonable stable performance would really help.
P.S. Forcing connections to 100mbps returns same performance for large and small file size as the old fast ethernet LAN.

Thanks

 

[brianinms]

You bought one of the cheapest gigabit switches known to man and are asking why is isn't performing well?

 

[heyvern]

OK thanks brianinms for not helping with the question. I did not ask what I could have bought but just what I might do help with what I have. By the way, I get essentially the same throughput when connecting 2 machines directly together w/o the switch so I don't really think the switch is relative to the particular problems I am seeing with the small file transfer time. So again what machine registry or NIC card settings might help and what addl info could I provide anyone who actually has something constructive to say.

 

[LawnBoy]

My bet is on IPX as the culprit. Disable it temporarily and run your peer-to-peer test again.


"We must fall back upon the old axiom that when all other contingencies fail, whatever remains, however improbable, must be the truth." - Sherlock Holmes

 

[heyvern]

Thankx LawnBoy, I have tried eliminating all protocols except tcp/ip for testing purposes. During measured testing with ttcp the numbers are about the same, real world drag and drop testing of the small files is still painfully slow. I just downloaded some 8169 reference drivers from realtek and will update some machines for further testing. One suggestion from another board was to turn off flow control on the nic's advanved properties. I will also try some experimenting with jumbo frames although cpu usage has never exceeded about 25% so I don't know how much that might help. I am still looking for recommendations of Tx and Rx window sizes. There are a lot of great tools out there for tweaking these settings for WAN and high latency networks but not for high speed low latentcy LANS. Suggestions still welcome.

 

[jimbopalmer]

At gigabit speeds, ALL networks are high latency.

Getting RWIN up to at least 29200 on the Win98 and 2000 boxes will surely help. (20 frames) As a general rule, the transmit window is sized to the other computer's RWIN.

I tried to remain child-like, all I acheived was childish.

 

[LawnBoy]

I've not had to tweak a Gig LAN so I can't help with the window sizes, sorry. You should not need to mess with jumbo frames to fix this problem.

At this point my only suggestion would be to try some different NICs.


"We must fall back upon the old axiom that when all other contingencies fail, whatever remains, however improbable, must be the truth." - Sherlock Holmes