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

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

Post by Bob Sha » Fri, 14 Jun 1991 13:55:54




>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.
--



IBM Champaign

 
 
 

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

Post by Chuck Henk » Fri, 14 Jun 1991 15:48:46


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?

And, why doesn't this work:

backup -0 -b 126 -f - /u | rsh rs2 dd of=/dev/rmt0 obs=126

The dd dies immediately with "invalid argument to system call" or
somesuch. In fact, I can't get dd to write on the tape at all.

--
| Chuck Henkel                      |                           |
| Department of Nuclear Engineering | Support nuclear power.    |
| N.C. State University             |                           |


 
 
 

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

Post by Fred L. Johns » Sat, 15 Jun 1991 00:04:32



...

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

...
> And, why doesn't this work:

> backup -0 -b 126 -f - /u | rsh rs2 dd of=/dev/rmt0 obs=126

> The dd dies immediately with "invalid argument to system call" or
> somesuch. In fact, I can't get dd to write on the tape at all.

The dd is dying because of the obs=126.  This is telling dd to use 126 byte
blocks for its write system call.  The 1/4" tape only accepts i/o requests
in multiples of 512 bytes, hence the EINVAL returned to dd from the write
system call.

Using 126b would tell dd to use a block size of 126, 512 byte blocks, and this
should make the tape device driver happier.

- Fred

My remarks and opinions are mine alone...
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"rdump" only writes half as much data as "backup"

Post by Mark R. Ludw » Sat, 15 Jun 1991 07:22:33



>backup -0 -b 126 -f - /u | rsh rs2 dd of=/dev/rmt0 obs=126

>The dd dies immediately with "invalid argument to system call" or
>somesuch. In fact, I can't get dd to write on the tape at all.

I *do* hope you mistyped your post and had

        obs=126b
               ^
or
        obs=126k
               ^
or something more than 126 bytes!  On the other hand, I tried this and
got:

        dd: 0511-053 The write failed.
        : Invalid Argument

so maybe you did.  In that case, I suggest you try a larger blocksize.$$
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