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Conference smurf::ase

Title:	ase

Moderator:	SMURF::GROSSO

Created:	Thu Jul 29 1993
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	2114
Total number of notes:	7347

2097.0. "Memory channel: how to copy a large table?" by ROM01::OLD_CIPOLLA (Bruno Cipolla) Thu May 29 1997 10:26

    i am evaluating the possibility to "reflect" a large (4Gbytes) 
    table in central memory from one system to another using the memory
    channel driver.
    
    I can afford to freeze updates being done to the primary table 
    for several seconds, in order to allow for "reflecting" the whole
    primary table to the second system.
    
    Do we have any examples/hints on how this can be done?
    
    any tricks?
    Bruno

T.R	Title	User	Personal Name	Date	Lines
2097.1	need segmentation and locking?	HERON::BLOMBERG	Trapped inside the universe	`Thu May 29 1997 11:43`	15
	You say "several seconds", but at 50 MB/s it would take 80 seconds to reflect the whole table. Can you really freeze the updates for that long? Otherwise you probably have to divide your table into segments and only do periodic updates of "dirty" segments. Another issue, is the target table consistent during the copy? Otherwise you have to lock it on the target system until the copy has completed (DLM?). /Ake
2097.2	two memory channels? PVM?	ROM01::OLD_CIPOLLA	Bruno Cipolla	`Fri May 30 1997 11:25`	10
	i think i can wait 80 seconds, how about two memory channels working in parallel? the target table is locked, it is just a shadow table just in case the primary system fails. i am considering using PVM (parallel Virtual Machine) to do the copy did anybody do this before? BC
2097.3	dpvm!	HERON::BLOMBERG	Trapped inside the universe	`Fri May 30 1997 11:46`	5
	I've used PVM, and in particular dpvm, which is optimised for memory channel. Check out http://tc-www.ilo.dec.com/. /Ake
2097.4		KITCHE::schott	Eric R. Schott USG Product Management	`Sun Jun 01 1997 16:04`	7
	The current released versions of MC driver do not support multiple active rails. This is being considered for a future release. Also, if the system does not have PCI bandwidth for multiple rails, having multiple active won't change performance too much.