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

[Fred L. Johnson]

In article <HENKEL%NEPJT.91Jun12234846 at nepjt.ncsuvx.ncsu.edu>,
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
> 
...
> 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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