SCO UNIX cpio allows no valid backup?!

[Paul Slootman]

In article <1991May23.115825.47879 at cc.usu.edu> sl3h7 at cc.usu.edu writes:
>cpio backup problems:
>
>How to get standard cpio package that will verify multiple tape
>backup?   On some systems, notably those using archive tape drivers,
>the second tape does not produce a valid verify -- bad magic
>error encountered.  I beleive that the tape driver is reporting
>that it does a write of the last block on the first tape when
>in fact it does not.  The verify passes the first tape, but
>after reading a bit of the second tape blows up with the
>"bad magic, out of sync " error.  This error may be avoided
[deleted]
>
>What is needed: a standard driver, cpio driver, that works 
>everywhere.

To answer the last question first: get afio. It generates archives
compatible with standard cpio; you can also tune the blocksize and
buffering to get the streamer tape really streaming. You can specify
the size of an archive volume, so that the tape is not written up
to the physical end of tape. That way you don't lose anything. We
use it on all the different systems we have.

However, in SCO Unix it is possible to specify options to cpio that
does the same as afio: use -K _kb_ to specify the size of an archive
volume in kilobytes, -C 5120 to specify block sizes of 5K,
-O /dev/rct0 or whatever to write to (instead of ... > /dev/rct0).
Check out the manpage for specifics. You can also specify -k when
reading a tape to skip corrupt bits, i.e. to read a tape with some
data missing. It should go on and search for a magic number, and
resynchronize.
For the size, take a 5% margin of error. Play around with the block
sizes to get optimal throughput.

[personal note: I've never used it; I prefer using a command (afio)
that's available on all systems I plan to use]

Hope this was helpful.

Paul.