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Use Caution when copying LMFS partitions (XL400/1200 Block Size)

    Date: Thu, 9 Apr 1992 02:16 PDT
    From: p2@porter.asl.dialnet.symbolics.com (Peter Paine)

	Date: Wed, 8 Apr 1992 18:23-0000
	From: smith@icat.larc.nasa.gov (Steven L. Smith)

	I want to save my lmfs.file.1 (not a file WITHIN the LMFS) file, however,
	I need to set the byte size in the file attribute. What is the byte
	size of a block for a XL400/1200? It's not the same for 3600 machines.

You mean the Length in Bytes attribute, accessible from dired by hitting the period key.

	Steve Smith                          | Internet: smith@icat.larc.nasa.gov
	NASA Langley Research Center         |
	M/S 152                              | Voice: (804) 864-2004
	Hampton, VA 23665                    | FAX  : (804) 864-7793

    Do a Dired of your Fep, pick the largest world.
    Divide the world byte size by its block size.

    For the 36xx machines (36 bit) (World - Genera-8-1)
      (floor 40950144 35547) => 1152
    For Ivory machines (40 bit)
      (floor 51759360 40437) => 1280

    Double check that you have not been doing funny things with the number
    base on the machine (ie. everything is in decimal).

The length of a FEP block  is the number words addressable by one byte, or 256 words.  
For an Ivory-based computer, with its 5 byte word, this is 1280.  For a 36XX, which has 
an even more exotic 4.5 byte word, a FEP block is 1152 bytes.

A LMFS FEP file is empty as far as the FEP file system is concerned, because its contents 
are manipulated "behind its back" by the LMFS program.  What Steven is proposing to do is 
to utilize FEP file system tools on an active LMFS.  THIS IS DANGEROUS!  You must make 
sure that NO LMFS modifications happen while you are copying the partitions, or you will 
end up with a corrupt LMFS.  You should disable services and shut down any mailer or print 
spooler.  The contents of LMFS partitions are a mysterious hash of data structures, and 
damage to one partition can corrupt the whole thing.