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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

1209.0. "DEMFA or DEFAA? that is the question" by WARNUT::FOSSEY (Does Water Run Off Your Head ???) Thu Jan 13 1994 12:51

    Can someone give me a performnace comparison between the DEMFA and
    DEFAA.
    
    I'm trying to decide which to configure into 4 x DEC 7000 which will be
    part of an FDDI VAXcluster running over 40Km's
    
    Regards,
    
    Laurence
T.RTitleUserPersonal
Name		DateLines
1209.1KONING::KONINGPaul Koning, B-16504Thu Jan 13 1994 15:205
You might ask the product manager (George Nielsen, I think).  Apart from any
performance differences, there's also likely to be a significant cost
difference...

	paul
1209.2George Nielsen's answerWARNUT::FOSSEYDoes Water Run Off Your Head ???Fri Jan 14 1994 16:2266
From:	DELNI::G_NIELSEN "GEORGE NIELSEN, NAC PRODUCT MANAGEMENT, DTN: 226-5510, MAIL: LKG1-2/W06  14-Jan-1994 1541" 14.JAN.94 21:26:29
To:	WARNUT::FOSSEY
CC:	G_NIELSEN
Subj:	DEMFA VS DEFAA

Laurence, see my replies below marked with "==>".

Regards

George

++++++++++++++++++++++++++++++++++++++=

From:	WARNUT::FOSSEY       "Laurence Fossey OLO DTN:851-1333, Does Water 
			      Run Off Your Head ???" 14-JAN-1994 14:42:15.88
To:	DELNI::G_NIELSEN
CC:	FOSSEY
Subj:	DEFMA v DEFAA

Hi George,

I'm in the process of configuring an FDDI VMScluster consisting of 
4 x DEC 7000-610's.

I have a choice of either DEFMA's or DEFAA's, can you can me any performance 
comparison information between these adapters?


==>	Operating either adapter in a standard FDDI ring, will deliver
	equivalent performance.

	The DEFAA is also available in a DAS configuration which allows
	it to be connected directly into an FDDI backbone without either
	a Wiring Concentrator or HUB.

	If however, you will be connecting these systems via a GIGAswitch,
	both adapters will initialize to full-duplex mode.  There is a 
	difference in the adapters full-duplex aggregate performance.  The 
	DEMFA will top end between 120 -> 130 Megabits/Sec, and the DEFAA 
	will top end between 140 -> 160 Megabits/Sec (max trans or receive
	is 100 Mb/Sec).

		This of course assumes that the host CPU has
		the cycles to drive the higher aggregate 
		bandwdith.

Which would you choose if money was no object?? 

==>	Add a FUTUREBUS+ backplane and use DEFAAs in conjunction with
	a GIGAswitch to build the cluster.

Is the difference in cost justified by the performance difference, bare in mind 
FUTUREBUS+ adapter which have to be purcahsed ???

==>	The DEMFA implements an older more costly technology.

	The DEMFA is only available as a SAS device, and can't/won't
	be upgraded to a DAS configuration.

I will post yopur answer in UPSAR::FDDI topic 1209 if that is OK with you ?

==>	OK

Regards,

Laurence Fossey