"rdump" only writes half as much data as "backup"

[Bob Shair]

henkel%nepjt at ncsuvx.ncsu.edu (Chuck Henkel) writes:

>Context: Two RS/6000 Model 320s running 3001.
>	 Tape drive configured for 512 byte blocks, no ECC

>I'm trying to use rdump to back up a filesystem on "rs1" to a
>cartridge tape on "rs2":

>rdump -0 -c -f rs2:/dev/rmt0.4 /u

>only writes about 10 meg on the tape, then asks for another. If I use
>a high density tape, (3M 6150, /dev/rmt0), it only puts about 20 meg
>on the tape, then asks for another.

>The "-b" flag (blocksize) has no apparent effect. Backing up
>filesystems on rs2 (the machine with the tape) works fine.

>What's the deal?

The deal is we accidentally omitted the -d (density) and -s (size)
flags from the man pages for rdump when we shipped AIX 3.1;  they're
in updated versions.

For a DC600A 120MB tape (rmt0.4) specify -s 9000 -d 1250
I append the appropriate Flags from 3.1.5 manual.
 

  rdump Command
  
   Syntax
  
  rdump [ -b Number1 ] [ -c] [ -d Number2 ] [ -l Number3 ]
  [-s Number4 ] [ -u] [ -w] [
  -W] [ -Level]  -f Machine:Device  [ FileSystem]
  Flags
  
  -b Number1	Specifies the number of blocks to write in a single
  output operation.  If you do not specify the Number1 parameter,
  the rdump command uses a default value appropriate for the physi-
  cal device selected.  Larger values of the Number1 parameter,
  result in larger physical transfers to tape devices.
  
  -c	Specifies that the tape is cartridge, not nine-track.
  
  -d Number2	Specifies the density of the tape in bits per inch
  (BPI).  This value is used in calculating the amount of tape used
  per volume.  If you do not specify a value for the Number2
  parameter, the rdump command uses a default density of
  1600 BPI.  For a default density of 8000 BPI, specify the -c
  flag.
  
  -l Number3	Uses the Number3 parameter as the limit of the total
  number of blocks to use on the remote backup medium.
  
  -s Number4	Allows you to specify the size of the tape in feet us-
  ing the Number4 parameter.  If you do not specify a tape size,
  rdump defaults to a tape size of 2300 feet.  For a de-
  fault size of 1700 feet, use the -c flag.  When the tape drive
  reaches the specified size, the rdump command waits for the tape
  to be changed.
-- 

Bob Shair                          shair at chgvmic1.vnet.ibm.com
Scientific Computing Specialist    SHAIR at UIUCVMD (bitnet)
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