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Conference 7.286::fddi

Title:FDDI - The Next Generation
Moderator:NETCAD::STEFANI
Created:Thu Apr 27 1989
Last Modified:Thu Jun 05 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2259
Total number of notes:8590

527.0. "ultrix,fddi,performance" by CSC32::HEINZ () Thu Apr 02 1992 18:18

    
    i have a customer that has 2 ds5000 -- he ran a ftp test (copied large
    file) with standard thinwire and then hooked up fddi and did same ftp
    test and it took 1 second longer --- i have no clue as to what we are
    looking at here but should it run faster or are there tons of
    underlying things i don't know about -- is there any test that he can
    run to see the performance increase..... ultrix v4.2a
T.RTitleUserPersonal
Name		DateLines
527.1KONING::KONINGPaul Koning, A-13683Thu Apr 02 1992 18:535
FTP could easily be disk bound.  Apart from that, is your MTU 4500, or 1500?
If you have the MTU set at Ethernet size, your performance won't be nearly as
good as it is with full-size messages.

	paul
527.2This is a guessSTAR::SALKEWICZIt missed... therefore, I am Thu Apr 02 1992 20:338
    Well,. on that platform, unless I'm mistaken (which could be) the
    Ethernet subsystem has DMA in both directions,.. but the FDDI
    subsystem (DEFZA) has DMA in ony one direction (receive),..
    So there is the potential for this to become CPU bound on FDDI
    where it was 'something-else'-bound on Ethernet.
    
    						/Bill
527.3Same type problemDENVER::PEACHTue Apr 07 1992 15:3119
    I have a customer that is experiencing same type problem only with NFS
    writes over FDDI.  Even with Eric Schott's IOenhancers for ULTRIX I can
    only write ~ 170k MB/sec.  
    The config is 1 DECsystem 5000/200 server and 5 DS5000/200 pxg with
    swap disk.  Each PXG has it's own RZ57 on the server.  The config
    includes both ethernet and FDDI.  All systems are running ULTRIX 4.2
    
    A DEC concentrator 500 handles connections from DS's to server.
    
    BTW, the IO enhancers increased performance ~400% on writes to scsi
    disks from server.
    
    The customer wants the problem escalated ASAP.  Any suggestions before
    this happens???
    
    Bob Peach
    Sales Support  Los Alamos National Lab
    DTN 480-2011
527.4addendumDENVER::PEACHTue Apr 07 1992 17:3323
    re .3
    Sorry...that was supposed to read "~170k bytes/sec".
    
    Other pertinent info:   MTU = 4500 for fddi
                            SO_SNDBUF upped to 2002
                            SO_RCVBUF upped to 2004  (as far as I could go
                            with these values before kernel would not
                            boot)
    
                            udp_cksum 0
    
    Ran netstat -s -i and according to analyst at CSC, no problems exist
    with FDDI that netstat could see.
    
    What else should I look for???
    
    thanks in advance,
    
    Bob
527.5Any update on this FDDI-FDDI performance issu ?ANTIK::WESTERBERGStefan Westerberg DS StockholmMon Nov 02 1992 12:499
Hi, I have a customer with a similar problem. When he do a FTP over FDDI from
one DECstation 5000-240 with a RZ58 disk to another 5000-240 with the same types
of disk the performance is 600kbyte/s. If they do the same test over Ethernet
they get 500 kbyte/s. The Mtu size one fza0 is 4352. If they do the same test
to a Silicon grafic host on FDDI they get 1200kbyte/s.

Any ideas on why the performance increase isn't bigger when switching to FDDI ?

/Stefan